||utnam's dltmenftag Stitna truits. INORGANIC CHEMISTRY: FOR USE IN SCIENCE CLASSES AND HIGHER AND MIDDLE CLASS SCHOOLS. BY DR. W. B. KEMSHEAD, F.R.A.S., F.G.S., LECTURER ON CHEMISTRY AND NATURAL SCIENCE, DULWICH COLLEGE, LONDON; AND EXAMINER IN CHEMISTRY, COLLEGE OF PRECEPTORS, LONDON. NEW YORK: G. P. PUTNAM'S SONS, FOURTH AVENUE AND TWENTY-THIRD STREET. TO TIiE trb. a. Z. (Crber,..B., Master of Dulwich College, TIIIS LITTLE WORK IS RESPECTFULLY INSCRIBED, AS A SLIGIT RECOGNITION OF PAST KINDNESSES AND COURTESIES RECEIVED BY THIE AUTHOR. P REFACE. TIE following work does not pretend to be a complete text-book on the science of INORGANIC CHEIISTRY, or even on that portion of it which would confine itself to the Non-metals. Written with an especial purpose, viz., for the use of pupils preparing for the First Stage, or Elementary Examination of the Science and Art Department, South Kensington, it necessarily confines itself to the subjects prescribed in the Syllabus of that Examination. My aim throughout has been to express, in as clear and simple language as possible, the earlier principles of the science, so as to fit the book for the use of mere beginners, but at the same time to be sufficientiy full and accurate that it might be useful as a text-book in the hands of more advanced students. The limits to which this series is confined have prevented me from giving all the experimental illustrations I could have wished; but I have, I trust, given amply sufficient to illustrate every assertion in the text, and have sought to make choice of those which, while they are striking and conclusive, combine also the property of being easily performed, and are therefore most suitable to students whose command of apparatus may be limited. 6 PREFACE. I make no apology for introducing the Graphic Formulae and Notation in so elementary a work. Independently of my own proclivities in its favour, the examination for which this book is specially prepared demands a knowledge of the theory of atomicity and of its graphic representation-to have omitted it, therefore, would have been impossible. For the benefit of those teachers who may not have adopted it, I have in all cases added the equations in the ordinary symbols as used by the late Professor Miller, Professor Williamson, &c. I have to offer my warm acknowledgments to Professor Frankland for the ready and kind manner in which he gave me permission to make free use of his valuable work, Lecture Notes for Chemical Students. *The elementary character of the work did not admit of much originality, except perhaps in the matter of arrangement; and I must here acknowledge my obligations to the works of Faraday, Miller, Williamson, Bloxam, &c., &c. The work while in the form of notes has done good service in preparing my own pupils for the South Kensington Examination; I trust it may be equally successful in the hands of those teachers who may adopt it. W. B. KEMSHEAD. DULWICH COLLEGE, LABORATORY, DULWICH, September, 1873. CONTENTS. CHAPTER I. Matter and Force-Physical Forces-Definition of Chemis'rySimple and Compound Matter-Metals and Metalloids or Non-Metals-Symbols-Atomic Weights-List of Elements -Physical Condition of Elements-Distribution of Elements,.,... Pages 9-16. CHAPTER II. Difference between Mechanical Mixture and Chemical Compound -Characteristics and Different Mlodes of Chemical ActionSummary,...... Pages 16-26. CHAPTER III. Combining Weights-Laws of Chemical Combination-Outline of Atomic Theory-Combining Volumes-Volume Weights, Pages 26-38. CHAPTER IV. French and English Systems of Weights and Measures-Conversion of English into French Weights and Measures-The Crith and its Uses,... Pages 38-43. CHAPTER V. Principles of Chemical Nomenclature-Classification of Elements into Positive and Negative-Symbolic Notation-Chemical Formulae-Chemical Equations,.. Pages 43-53. CHAPTER VI. Atomicity of Elements-Classification according to AtomicityGraphic Notation-Simple and Compound Radicals-Definition of a Compound Radical,.,. Pages 53-65. CHAPTER VII. Hydrogen-Its History-Distribution and Natural HistoryPreparation-Properties —Combinations,. Pages 66-82. CHAPTER VIII. Chlorine-History-Distribution and Natural History-Preparation-Properties —Combinations,.. Pages 82-90. 8 CONTENTS. CHAPTER IX. Hydrochloric Acid-History-Distribution and Natura. l History — Preparation-Properties-Combinations,. Pages 93-98. CHAPTER X. Oxygen-History-Distribution and Natural History-Preparation-Properties-Allotropic Oxygen or Ozone, Pages 98-111. CHAPTER XI. Combinations of Oxygen-Formation and Reactions of WaterPreparation and Properties of Hydroxyl-Compounds of Chlorine with Oxygen and Hydroxyl, Pages 112-129. CHAPTER XII. Boron-History-Its Occurrence in Nature-Its Allotropic Modifications-Boric Anhydride-Boric Acids,. Pages 129-133. CHAPTER XIII. Carbon - Preparation- Allotropic Forms - Combinations -Preparation and Properties of Carbonic Oxide-Carbonic Anhydride, its Preparation and Properties,. Pages 133-145. CHAPTER XIV. Nitrogen-Its Preparation and Properties-Compounds of Nitrogen with Oxygen and Hydrogen-Compounds of Nitrogen with Hydrogen-Amnmonia-Ammonic Salts, Pages 145-156. CHAPTER XV. Compounds of Nitrogen with Hydrogen-Ammonia-Its History, Preparation, and Properties - Ammonium - Ammonic Salts,...... Pages 156-163 CHAPTER XVI. Sulphur —Iistory -Occurrence-Preparation-Properties- Allotropic Modifications-Uses-Compounds of Sulphur with Positive Elements-Sulphuretted Hydrogen-OccurrencePreparation - Properties - Reactions-Uses - Hydrosulphyl -Carbonic Disulphide-Properties-Reactions, Pages 163-169. CHAPTER XVII. Compounds of Sulphur with Oxygen and Hydroxyl, Pages 169-183. INORGANIC CHEMISTRY. CHAPTERI I. Matter and Force-Physical Forces-Definition of ChemistrySimple and Compound Matter-Metals and Metalloids or Non-Metals-Symbols-Atomic Weights-List of Elements -Physical Condition of Elements-Distribution of Elements. WE shall the better understand the full definition of the science of Chemistry, if we first explain some of the terms which we are compelled to make use of. Of these terms the two most important for us clearly to understand are matter and force. 1. Matter is the name which we give to all things which exist, or which can in any way be recognized by our senses; thus, the earth we live on, the water we drink, the air we breathe, the bodies we dwell in, are all material, or, scientifically speaking, masses of matter. Matter possesses various properties, but the essential ones (without which, in fact, it would not be matter) are, that it must possess weight and occupy space. All matter is subjected to various influences, some of which impart to it new properties, without, however, changing its external form or appearance; others, while altering its external form, do not sensibly change it in other respects; while another, that with which we are more directly concerned, not only alters matter in external form, but in nearly all cases imparts to it totally new and different properties. These various influences are called forces, and are divided into physical or natural and chemical forces 10 INORGANIC CIIEMISTRY. e. g., if a bar of iron or any metal be heated, it will bee come visibly, sensibly larger; and if the heat be sufficiently great, it will pass from the solid to the liquid form, but it will still remain iron, or copper, or brass, &c., as the case may be. Heat, therefore, simply changes its size and condition, but not its nature. EXPERIMENT 1.-Thus, if some water be put into a Florence flask, and heat be applied by means of a spirit lamp or Bunsen burner, the water will be converted into vapour which will be invisible; but if an arrangement similar to that shown in Fig. 1, where A is a retort in which the water is heated; B, a receiver, kept cool Fig. 1. by a constant supply of cold water kept up over the outside; and C, a vessel to receive the water thus condensed, the vapour will be again converted into water, from which it started. If now some water be put in a metal vessel-a tin, or zinc, or pewter pot, and the whole then immersed in a mixture of broken ice and salt, the water will gradually contract or diminish in volume, until it reaches a temperature a little above freezing point (4~ C. or 39'2~ F.), when it expands, and continues to do so until the moment of solidification, when it expands suddenly and violently to 1 of its former bulk, and finally it will be converted into a solid mass of ice. But whether it be in the condition of vapour or gas, the liquid water, or the solid ice, it is still the same chemical substance-water (OH2). EXP. 2.-If some iodine be put in a Florence flask, and a gentle heat applied, the iodine will not melt, but will at once be converted into a beautiful rose-coloured vapour, which will be again condensed into minute crystals of iodine in the upper or cool part of the flask. COMPOUND BODIES. 11 These experiments show that heat may alter the size and physical condition of a substance; but, especially if the substance be a simple one, it does not alter its nature. Again, if a rod of sealing wax or glass be rubbed with a piece of warm dry flannel or silk, they will undergo no apparent change of any kind, but they will be found to have acquired the property of attracting to themselves all light substances. This property we call electricity. Further, if a bar of steel or a steel needle be rubbed with a piece of loadstone, it will present the same appearance; but if suspended, so as to be free to move, it, will now always point in one direction-it is, in fact, under the force of magnetism. But if we put together some iron or copper filings and sulphur, and expose the mixture to heat, the metal and the sulphur will combine, and a third substance will be formed which will be found to possess properties totally distinct from those of the metal or sulphur employed. The force under which this combination takes place is called chemical force. 2. Chemistry, then, is the science which treats of matter (i. e., of all bodies whatsoever which have been or can be subjected to man's investigation) in respect of its nature, its composition, and its properties. It investigates the mutual relations of different masses of matter, and their actions on each other when under the influence of this chemicalforce. 3. Simple and Compound Matter.-One of the first properties of matter which forces itself on the attention of the chemist is, that it is either simple or compound in its nature. 4. By simple bodies or elements we are to understand those which we are not able by any means we have at our command to split up into two or more different substances. Thus, sulphur is an element; by no process whatever can we obtain anything but sulphur from it. Mercury, copper, iron, and gold are all simple substances or elem.ents. 5. By compound bodies we mean all those which, under the treatment of the chemist, can be made to yield 12 INORGANIC CHEMISTRY. more than one simple or elementary body-e. g., chalk is a compound; under suitable treatment it can be made to yield an invisible gas called oxygen, a black solid-carbon, and a white shining metal-calcium. So, sugar is a compound, and may be resolved into two gases-oxygen and hydrogen, and a solid-carbon. Brass is a compound, and may be divided into the two metals, zinc and copper. NOTE.-All compounds formed by the union of two or more metals are called alloys, unless mercury be one, in which case they are called amalgams. Of these elements chemists have ascertained the existence of sixty-two or'sixty-three. These have been again subdivided into two classes-non-metals or metalloids, and metals. NOTE.-The former term, although not so convenient, because a compound word, is more correct, and is now universally employed. 6. Characteristics of YMeta3l and Non-Metals.-The metals are generally known as possessing a peculiar lustre called metallic, a high specific gravity, or great density, and for being good conductors of heat and electricity; while the non-metals are noted for the absence of this metallic lustre, their generally low specific gravity, and for their being generally bad conductors of heat and electricity. The above definition, though perhaps the best that can at present be given, is not at all satisfactory; for, with respect to lustre, many of the metals possess it only in a modified degree, and some lose it altogether when reduced to powder; while one of the non-metals, iodine, possesses it in a very remarkable degree. Again, with respect to density or specific gravity, while it is true that the metals for the most part are heavy, while the metalloids are light, it is not universally the case; for three of the metals —lithium, potassium, and sodium-are lighter than water;. and several of the non-metals-bromine, selenium, iodine, arsenic-have a density from three to five times that of water. SYMBOLS-ATOMIC WEIGHTS. 13 In like manner, the power of conducting heat and electricity, although distinctive of, is not absolutely confined to, metals. 7. Symbols.-Instead of writing the whole name of an element, chemists are in the habit of using merely the initial letter, or, in the case of two or more elements beginning with the same, the more common or more important one has the initial; while the other elements are distinguished by the addition of a small letter, thuscarbon (C), calcium (Ca), chlorine (Cl), cobalt (Co), cuesium (Cs), and so on. 8. Atomic Weights.-It is found by experiment that whenever substances, either elementary or compound, unite together chemically, they always do so in certain fixed definite proportions. These proportions by weight, when reduced to their lowest relative value, and expressed with reference to that of hydrogen, which is usually taken as unity, are called the atomic weights, or combining nambers, of the elements. Thus, the symbols not only indicate the elements which they represent, but they also stand for a fixed definite proportion by weight of that element. Subjoined is a list of the elements, with their symbols and atomic weights, or combining numbers: Names of Elements. Symbols. Atomic Weights. Aluminium,..................... Al. 27'5 Antimony (Stibium)......... Sb. 122 Arsenic,.......................... As. 75 Barium,..................... Ba. 137 Bismuth,....................... Bi. 210 Boron,........................... B. 11 Bromine,........................ Br. 80 Cadmium,....................... Cd. 112 Caesium,................... Cs. 133 Calcium,......................... Ca. 40 Carbon,.......................... C. 12 Cerium.......................... Ce. 92 Chlorine,..................... C1. 35 5 Chromium,................. Cr. 52'5 Cobalt.................... Co. 59 Copper (Cuprum),........... Cu. 635 Didymium,............ Di. 5 14 INORGANIC CHEMISTRY. Names of Elements. Symbols. Atomic Weights. Erbium,...................... E. 112-6 Fluorine,................. F. 19 Glucinum or Beryllium,.... G. or Be. 9-3 (?) Gold (Aurum).............. Au. 196-6 Hydrogen,................... H. 1I Indium,................. In. 113'4 Iodine............................ I127 Iridium,...................... Ir. 197 Iron (Ferrum),................. Fe. 56 Lanthanum...................... La. 92 Lead (Plumbum)............. Pb. 207 Lithium......................... Li. 7 Magnesium,.................... Mg. 24 Manganese..................... Mn. 55 Mercury (Hydrargyrus),.... Hg. 200 Molybdenum,................. Mo. 96 Nickel,...................... Ni. 59 Niobium or Columbium,.... Nb. 97-5 Nitrogen,..................... N. 14 Osmium........................ Os. 199 Oxygen........................... 16 Palladium....................... d. 106-5 Phosphorus,.................... P. 31 Platinum,....................... Pt. 197'4 Potassium (Kalium)......... K. 39 Rhodium,........................ Rh. or Do. 104 3Rubidium,..................... Rb. 85'5 Ruthenium,.................. Rlu. 104 Selenium,...................... Se 79 Silicon or Silicium,.......... Si. 28-5 Silver (Argentum),............ 108 Sodium (Natrium),...........Na.23 Strontium,.................... Sr. 87'5 Sulphur,........................ S.32 Tantalum,...................... Ta. 1375 Tellurium,................. Te. 128 Thallium,....................... T1. 204 Thorinum,.................... Th. 231'5 Tin (Stannum),................ Sn. 118 Titanium,....................... Ti. 50 Tungsten (Wolfram),....... W. 184 Uranium,...................... 120 Vanadium...................... V. 137 Yttrium,........................ Y. 68 Zinc.............................. Zn. 65 Zirconium,.................... Zr 6895 DISTRIBUTION OF ELEMENTS. 15 9. Non-Metals.-The following thirteen elements are universally admitted as non-metals:Hydrogen,........ H. 1 Boron,............. B. 11 Oxygen,........... 0. 16 Iodine.............. I. 127 Nitrogen,........... N. 14 Phosphorus....... P. 31 Chlorine,........... C1. 35-5 Sulphur,.......... S. 32 Fluorine,........... F. 19 Selenium,......... Se. 79 Bromine,.......... Br. 80 Silicon,............ Si. 28'5 Carbon,............. C. 12 To these the majority of chemists add tellurium (Te, 128) and arsenic (As, 75). The remainder of the elements are metals. 10. Physical Condition of Elements.-Under the ordinary circumstances of temperature and pressure, the following five elements are gaseous, viz.; oxygen (0), hydrogen (H), nitrogen (N), chlorine (C1), and fluorine (F); while bromine (Br) and mercury (Hg) are liquid, and the remainder are all solids. 11. Distribution of Elements.-The following twelve elements constitute the chief part of the earth, whether of the solid ground, the sea, the air, or the animals and vegetables that inhabit them; they are consequently the most abundant: Hydrogen,...............H Silicon,................. 8S Oxygen.................. 0. Aluminium,.......... Al. Nitrogen,.............. N. Calcium,................. Ca. Carbon............... C. Iron,......................e. Chlorine,............... C1. Potassiumn,............. K. Sulphur,............... S. Sodium,.............. Na. The next eleven elements, although not so abundaht, are either of frequent occurrence, or of great chemical importance. They are:Bromine,............... Br. Manganese,......... Mn Copper.................. Cu. Mercury,............. Hg. Fluorine................ F. Phosphorus,........ P. Iodine,................... I. Silver,................... Ag. Lead,.................... Pb. Zinc,.................... Zn. Magnesium,............ Mg. 16 INORGANIC CHEMISTRY. The next group of eighteen elements may be regarded as of secondary importance, viz.:Antimony............... Sb. Nickel.................. Ni. Arsenic,................ As. Palladium.............. Pd. Barium.............. Pa. Platinum,..Pt. Bismuth,.............. Bi. Rhodium,............... Rh. Boron,................... B. Strontium,.............. Sr. Chromium,........... Cr. Tin........................ Sn. Cobalt,................. Co. Titanium............... Ti. Gold...................... Au. Tungsten,.............. W. Iridium,.............. Ir. Uranium,......... U. The remaining elements may be regarded as those of very rare occurrence, or of which our knowledge is yet very imperfect. Some of them, indeed, as erbium, indium, &c., are at present merely chemical curiosities. CHAPTER II. Difference between Mechanical Mixture and Chemical Compound -Characteristics and Different Modes of Chemical Action -Summary. 12. WE have defined "a compound body" to be one which we can decompose into two or more simple bodies or elements; but in considering this definition it is important to distinguish clearly between a mere mechanical mixture and a chemical compound, for the effects produced by mixture and by combination are exceedingly different. 13. Properties of a Mechanical Mixture.-In a mixture, the materials may exist in any proportion whatever, and the properties of the mixture will partake of those of each of its constituents; while in a chemical compound combination will only take place in certain fixed, definite, and unalterable proportions, and the resulting compound will PROPERTIES OF A MECHANICAL MIXTURE. 17 possess properties totally distinct from those of either of its constituents. EXP. 3.-If iron filings and powdered sulphur be mixed together, they may be so in any proportion whatever, and the resulting mixture will retain in a modified form the characteristics of both. Thus the inflammability of the sulphur will be modified by the non-inflammability of the iron, and the power of conducting electricity which the iron possesses will be modified by the presence of the sulphur, which does not possess this power; but the iron and the sulphur will still exist independent of each other, as may be shown by drawing a magnet several times through the mixture, when the iron filings will adhere to the magnet, and the sulphur be left behind. EXP. 4.-Sand and sugar may be mixed together in any proportions, and the resulting mixtures will possess both the grittiness of the sand and the sweetness of the sugar, each in a modified form; but no action having taken place between them, they may be easily separated by the mechanical act of solution and filtration. The sand will be left behind on the sieve or filter. Gunpowder affords an exceedingly good instance of the difference between the effects of mechanical mixture and chemical combination. It is made from saltpetre or nitre (nitrate of potassa), charcoal, and sulphur, which are mixed together by mechanical means in the most intimate manner possible; but no chemical action having taken place between them, they still remain separate and distinct. The nitre may be washed out by means of water, and by evaporating the water may be again obtained in the solid form. So in like manner the sul#phur may be washed out by carbonic disulphide, and on allowing the disulphide to volatilize, the sulphur may be obtained, while the charcoal remains behind undissolved. If, however, we cause the materials to enter into true chemical combination, all is changed-the mixture is fired by heat, the dormant chemical force is called into being, the three solids disappear and are suddenly converted into an enormous volume of gaseous matter, and new substances are produced, possessing properties totally distinct from those of either the nitre, sulphur, or charcoal. It is the study of this chemical force, and of the laws 10 E. B 18 INORGANIC CHIEMISTRY. which govern its action, which is especially the province of Chemistry. 14. Characters of Chemical Action.-Chemical attraction or affinity is distinguished from all other kinds of force by several well-marked features. 1. It acts only between particles which are absolutely in contact. It is rarely possible, by mechanical means, to bring the particles in sufficiently close contact for chemical action to commence; recourse is generally had to solution, or fusion, or chemical means. ExP. 5.-Mix together I oz. sodic carbonate and 1 dram iartaric acid, no action takes place, not even if the mixture be ground in a mortar; now place it in a glass and add water, a brisk effervescence ensues, due to the chemical action set up, and the escape of a gas called carbonic anhydride. EXP. 6.-Mix together iron filings and powdered sulphur, no action takes place; put them in a crucible and apply heat, so as to melt the sulphur, combination ensues, attended with a great manifestation of heat. EXP. 7.-A mixture of oxygen and hydrogen gas, in the proportion of one volume of oxygen to two volumes of hydrogen, may be made, and left in a soda-water bottle for any length of time, no action will take place between them; but, if an electric spark be passed through, or a light be applied, combination takes place suddenly, and with great violence. Some solids appear, at first sight, able to act chemically on each other, e.g. - EXP. 8.-When iodine is sprinkled over phosphorus, combination instantly takes place, attended with the evolution of light and heat; but, in this case, both substances are volatile, and the commencement of the action takes place between their vapours. 2. Chemical action is most strongly exerted between dissimilar substances." Thus, no action whatever takes place between two pieces of iron, or two pieces of copper, or two pieces of sulphur; but between iron and sulphur, or copper and sulphur, very intense chemical action will take place. * This circumstance-viz., that chemical action is strongest between unlike substances-makes the term "affinity," which is commonly employed to express " chemical action or attraction," an objectionable one. CIIARACTERS OF CHEMICAL ACTION. 19 As a rule, the greater the difference in the properties of two bodies, the greater is their tendency to mutual chemical action. Chemical union may. take place between bodies allied to each other in properties, but such unions are very unstable. 3. The most striking and characteristicfeature of chemical attraction is the entire change of properties with which it is attended, a change that by no possible reasoning could have been predicted. Under its influence solids are converted into liquids, liquids into solids, and gases into liquids and solids; while all the various changes of colour, taste, and smell, which we meet with on every hand, are entirely due to chemical force or attraction. ExP. 9.-Triturate or mix in a mortar some freshly crystallized sulphate of soda and carbonate of potash; the two solids will become converted into a liquid. EXP. 10.-Take a saturated solution* of chloride of calcium, and drop into it a small quantity of sulphuric acid; the two clear liquids will become converted into a white opaque solid. EXP. 11.-Make a strong syrup, by dissolving a small quantity (five or six lumps) of white sugar in a beaker glass, with a little warm water. Place the beaker glass in a soup plate or gas tray, and add gradually strong sulphuric acid, and stir; in a few minutes the clear syrup will blacken, begin to effervesce, and rise in the glass, and finally it will become solid (sufficiently so for the stirrer to stand upright), and flow over, filling the soup plate. The rationale of the above experiment is, that sugar is a compound of carbon, oxygen, and hydrogen, the two latter being always present in the proportion in which they would form water. Now sulphuric acid has the property of being very greedy of water whenever it meets with it, and it not only absorbs the water which was used in converting the sugar into syrup, but also that which enters into the composition of the sugar itself, so that the carbon is set free, producing the solid mentioned. The reason of its occupying so large a space is, that, being in a very minute state of subdivision, it is exceedingly porous, and is largely permeated by the liquid and steam produced by the mixture of the sulphuric acid and water. * Solids do not dissolve in liquids in indefinite proportions; and, when the liquid has dissolved as much as it is capable of doing, the solution is said to be saturated. 20 INORGANIC CHEMISTRY. If the gases oxygen and hydrogen be mixed in the proportion of one of the former to two of the latter, and exploded in a suitable apparatus, water is produced. The full description of this will be given in Chapter IX. under the heading of water. ExP. 12.-Dip a clean feather into hydrochloric (muriatic) acid, and moisten with it the interior of a glass jar, cover immediately with a glass plate, and in like manner moisten the interior of a similar jar with...... ammonia; bring the two jars together mouth to mouth, but with the glass plate between them, they will both appear empty; but if the glass plate be removed, the whole included space will be filled with a dense white vapour, which at last settles on the sides of the jars in the form of I a white powder-solid chloride of ammonium. The changes of colour which take place i -l Ill under the influence of chemical attraction ^liiii S are so diverse that it is difficult to select ____^p^^^^^^^ instances for illustration, they are so abundant. The arts of dyeing and calico printing are entirely chemical ones. EXP. 13. —Take four conical test glasses, and in each put as follows:-In the first, a small quantity of argentic itate nitratetrate of silver); in the second, a small quantity of plumbic nitrate (nitrate of lead); in II II ^the third, some mercuric chloride; and in - 4lllll:!!^ _I the fourth, some chlorine water, to which -.-... —-r"- a few drops of a weak solution of starch ________ —__ has been added. (These salts should all' -- _ _ ~be in solution.) The liquids in the four glasses will all be colourless and clear like Fig. 2. water; now add to each a few drops of solution of potassic iodide. In the first glass, a pale yellow or straw coloured precipitate will be thrown down; in the second, a dark yellow, almost orange, precipitate; in the third, a brilliant scarlet precipitate; while the liquid in the fourth glass will be turned a beautiful blue. Many other beautiful and effective experiments on the changes of colour caused by chemical action will be met with in the course of reading this book. The common holiday trick of appearing to pour from a bottle,-previously filled with water,-milk, port, sherry, champagne, blue ink, &c., is done by the glasses being previously prepared with the necessary chemicals to produce the desired effect. CHARACTERS OF CHEMICAL ACTION. 21 The changes in taste and smell produced by chemical action are very striking, but do not so easily admit of experimental demonstration. Two examples may however be taken. EXP. 14.-Mix together in a mortar equal parts of ammonia chloride and quick lime, both of which substances are inodorous. The mixture disengages a gas possessing a most pungent odour. EXP. 15.-Chlorine is a gas, possessing highly irritating, pungent, and poisonous properties. Sodium is a metal of an exceedingly caustic and poisonous nature; and yet if they be caused to unite, they produce a white solid (common salt, chloride of sodium), not only not poisonous, but actually necessary to life. EXP. 16.-If 37 parts of hydrochloric acid be mixed with 41 parts of caustic soda, both of which substances are intensely poisonous, we shall obtain a neutral solution, consisting of 60 parts of common kitchen salt, dissolved in 18 parts of water. The only property which chemical action is powerless to alter or even modify is that of gravity or weight. 16 grs. or oz. or lbs. of oxygen will unite with 2 grs., oz., or lbs. of hydrogen, and produce exactly 18 grs., oz., or lbs. of water. So, in the conversion of iron into iron oxide or rust, 7 lbs. of iron require exactly 3 lbs. of oxygen, and produce 10 lbs. of iron rust. There is never a loss of weight in any chemical action. One of the great truths which Chemistry teaches is, that, under no circumstances whatever, can there be either creation or destruction of matter. In all cases in which the matter seems to be destroyed,-as the burning of a candle and other cases of combustion,-the destruction is apparent only; the matter under the influence of the chemical force is made to take the form of an invisible gas, and therefore appears to be lost. If, however, we take means to collect the products of the combustion, we shall find that so far from losing in weight, they weigh more than the original candle did, the increase in weight being due to the oxygen of the air consumed in the burning. The following simple experiment will show this - EXP. 17.-A glass tube (Fig. 3)-a common lamp glass does very well-with a cork fitted to the bottom, through which are several holes, in one of which a taper is fixed; the upper part of the lamp glass is connected, by india-rubber tubing, with a 22 INORGANIC CHEMISTRY. U-tube, in which is placed some caustic soda, the other branch of the U-tube is also connec3 ted with a water bottle, or aspirator. The lamp glass, with the candle, the connection, and the U-tube, withthe caustic soda, are then carefully weighed, and their weight,I*~ | |to the nearest grain accur*~I IH~ |ately noted. The connection with the water bottle being then made, the tap is turned on, and as the water runs out, the air passes up through the lamp glass, &c., to supply its place, and a current or draught E*till~~ ~ of air is thus established /rt f%\ ^ through the whole apparatus, the taper is then lit, and it and the cork quicklyreplaced. Fig. 3 When the taper has burnt for a few minutes, the water is turned off, and the taper almost immediately goes out. If, now, the tubes which were weighed at the beginning of the experiment, be again weighed, it will be found that although the candle is considerably less than it was at first, the tubes are perceptibly heavier. The rationale of the above experiment is this-the candle is a compound of hydrogen and carbon, the air is a mixture of two gases, oxygen and nitrogen; the burning of the candle, like all cases of combustion, is simply a case of chemical combination; so that, in the burning, the hydrogen (H) of the candle unites with the oxygen (0) of the air to form water (HI20) in the con-.li| i'..j..... i dition of steam, and the carbon'e i-.....( (C) of the candle unites with the I-,"'-'t ",:II:, X oxygen of the air to form carbonic J I"'"''~ D sk:. acid (CO0). These two invisible ^ gases, steam and carbonic acid, carried upwards by the draught, are caught and retained in the U-tube by the caustic soda with __g ) ^)__K Do~ ~which they enter into eager combination, and the whole apparatus weighs heavier than at first, by exactly the amount of oxyFig. 4. gen which has been abstracted from the air to form the steam and carbonic acid. CIARACTERS OF CHEMICAL ACTION. 23 That water and carbonic acid are produced when a taper or candle is burnt in the air may be shown by the following experiments:EXP. 18.-Hold over the flame of the taper or candle a cold, dry, bright, tumbler or beaker, the inner surface will at once become dimmed by the dew or moisture which will collect on it. The experiment might be arranged, by keeping the outside of the tumbler or beaker continually cool, so as to collect quite a wine glass of water from the burning candle. EXP. 19.-Let the taper be burnt in a clean glass bottle with a narrow neck, or with the neck nearly closed by having a piece of narrow glass tubing inserted through the cork. In a few minutes, according to the size of the bottle, the taper will burn dim, and finally go out. If, now, some lime water* be poured in, and the bottle be agitated, the lime water will be turned milky, indicating the presence of car- l bonic acid-the milkiness being due to chalk which is formed from lime and 1 carbonic acid. I I, 4. There are two modes of forming chemical compounds-the simplest, where two substances unite directly ii j1I together, as when hydrogen (H) is burnt in oxygen (0) and water is I formed, or where an acid and an I| l alkali, as hydrochloric acid (HCl) I and ammonia (H3N), unite together and form a salt. This only takes place when the bodies have a Fig. 5. powerful tendency to unite. The other and more common mode of combination occurs when one of the ingredients of a compound is displaced by another substance, and a new compound is the result; for example, if to a solution of nitrate of lime (which is clear and transparent as water) sulphuric acid be added, the sulphuric acid drives out the * Lime water may be made, by taking a piece of freshly slaked lime, about the size of a walnut, and putting in a wine bottle of distilled water, and shaking well. After standing twenty-four hours the clear liquid is fit for use. 24 INOlROANfO CHEMISTRY. nitric acid and unites with the lime, forming sulphate of lime, which, being insoluble, falls to the bottom of the glass as a solid white precipitate. 5. Whenever chemical combination takes place as the result of a direct union, heat is always given forth, and the quicker the combination takes place the greater is the heat evolved, in some cases rising so high as to give rise to ignition and combustion-since all solid substances, when heated sufficiently, become luminous. Exp. 20.-If water be poured on newly burnt lime, the lime swells, breaks into powder, and gives forth intense heat, sometimes sufficiently so to set fire to wood-work with which it may be in contact. Barges and houses have been frequently set fire to from this cause. EXP. 21.-Place in the bottom of a flask or testtube about ~ oz. of powdered sulphur, and above that put some copper turnings, previously made hot; now apply heat to the sulphur in the bottom of the flask, i61^^. 6.,, \which will melt, and finally boil. As soon as the vapour of the burning sul_F^ig.ill _SSSS phur reaches the copper, tne latter becomes red hot, burns with a lurid red light, melts, and falls to the bottom of the flask, uniting with the sulphur, and forming a black sulphide of copper. EXP. 22.-If a piece of the metal potassium, about the size of a pea, be thrown on the surface of cold water, it will combine with the oxygen of the water, setting free the hydrogen; and the combination will take place with sufficient intensity to set fire to the hydrogen, which burns with a pale violet flame, owing to the presence of a small quantity of the vapour of the potassium. 6. In a mechanical mixture, the proportion of the ingredients may be varied at pleasure, within all conceivable limits, while chemical action takes place only between certain invariable proportions of the constituents; thus, if mercury (Hg) be heated in oxygen gas, red scales will be formed on its surface (oxide of mercury), owing CHARACTERS OF CHEMICAL COMBINATION. 25 to its union with oxygen. If this red powder be collected and weighed, it will be found that for every 216 grains of the powder the mercury will have lost 200 grains in weight. If, as will sometimes under certain circumstances happen, a black powder be formed instead of a red one, then, on collecting the powder and weighing it, it will be found that the loss of the mercury is to the powder formed as 400 grains of mercury is to 416 grains of the black powder. In other words, the metal mercury can be made to unite with the gas oxygen, by the application of heat in the two following proportions:(1.) 400 parts of mercury will take up 16 parts of oxygen, and give rise to a black powder known as suboxide of mercury (HgO). (2.) 200 parts of mercury will unite with 16 parts of oxygen, giving rise to a red powder known as oxide of mercury (HO). But no power with which we are acquainted can make mercury and oxygen unite in other than these two proportions. 15. Summary of Chief Characters of Chemical Combination.-The leading characters by which chemical attraction is distinguished from all other forces may be thus summed up:16. "Chemical attraction is a power of extreme energy, which acts only on the minutest particles of matter, and at distances too small to be perceptible. Under its influence the elementary bodies, though comparatively few in number, arrange themselves into the numberless compounds which constitute the different forms of matter in the three great kingdoms of nature; and it is important to observe that the proportions in which they unite are fixed and invariable." That it takes place between different kinds of matter with different but definite degrees of force, and that, as a rule, the greater the difference between the substances the more intense is their chemical action on each other. That it is attended by a total change of properties, both physical and chemical, with the exception of that of 26 INORGANIC CHEMISTRY. gravity or weight. The compound resulting from a chemical union possesses properties totally differing from those of either of its constituents. The reason of gravity or weight remaining unaffected is, that in chemical action there is no loss, no destruction of matter, but merely a change of form. And, lastly, that where chemical action is the result, not of substitution, but of direct union of the elements, heat, and not unfrequently light, is manifested; the heat being in all cases a direct measure of the intensity of the chemical action which takes place. CHAPTER III. Coimbling Weights-Laws of Chemical Combination-Outline of Atomic Theory-Combining Volumes-Volume Weights. 17. Combining Weights.-In the last chapter it was stated as one of the peculiar features of chemical attraction that, when it took place, it only occurred between certain fixed, definite, invariable proportions of the constituents. These fixed, definite proportions, ascertained by the comparison of a large number of experiments, and reduced to their simplest and lowest expression, are called the combining weiglts of the substance. As it is necessary to have some standard to which to refer them, chemists are now nearly universally agreed to call the lowest proportion of hydrogen 1, and to refer the weights of all others to that scale. Thus, the combining weight of hydrogen being 1; that of oxygen becomes 16; of nitrogen, 14; of carbon, 12; of sulphur 32; of mercury, 200; of zinc, 65; of iron,. 56, and so on. A complete list of the combining weights of all the elements is given on pages 13 and 14, with the table of the elements. 18. Laws of Chemical Combination.-The relative LAWS OF CHEMICAL COMBINATION. 27 proportions in which the elements unite are regulated by fixed laws. These laws (four in number) form the basis of all chemical science, and regulate the mode of combination of every known chemical substance, simple and compound. They are called the laws of chemical combination. 19. Law 1.-This is called the law of constant composition, or law of definite proportions. It may be enunciated as follows:-" The same chemical compound always contains the same elements, united together in the same proportions." Thus, 100 parts of water always contain 88-8 (888) parts of oxygen, and 11i1 (111) parts of hydrogen. The weight of the oxygen is always eight times that of the hydrogen. It does not matter from what source the water is taken, whether it be from the melting of snow on the tops of the highest mountains, from rain clouds, from dew, or.from that obtained by chemical action, its composition is invariable. It is impossible for us to conceive water with the same properties as ordinary water, but having a different proportion of oxygen and hydrogen from that above given. So, also, a piece of flint or rock crystal, no matter where it may come from, will be always found on analysis to yield in 100 parts 46'6 parts of silicon, and 53'4 parts of oxygen. In fact, experiment shows that all true chemical compounds, which have been submitted to analysis, have a fixed definite composition. It is the generality and universality of this law thai give to analysis its practical value, since the results are always uniform and certain. The converse of this law, however, viz.: "That the same chemical elements united together in the same proportions will always produce the same chemical compound" -does not by any means hold good. 20. Isomerism.-A great many substances have been discovered amongst organic bodies composed of the same elements in the same relative proportions, and yet exhibiting physical and chemical properties perfectly dis. 28 INORGANIC CHEMISTRY. tinct one from another-e. g., oil of lemons, oil of turpentine, oil of rosemary, and many others all contain the same elements, united together in the same proportion; so the crystallized portion of essence of roses and common coal gas are chemically identical. To all such bodies the term Isomeric (from Loos, equal, and EuEOS, part) is applied. 21. Law 2, called the law of multiple proportions, may be thus enunciated-" tWhen two bodies are capable of uniting together in more than one proportion, these proportions will bear a simple ratio to each other." When simple elementary bodies unite in more than one proportion, the compounds so obtained will differ altogether in chemical properties, but there will be a regularity in the plan on which they are formed. Thus, if A and B be the elements in question, if A be constant, B will be found to exist in a series of multiples, such asA + B, A + 2 B, A + 3 B, A + 4 B, &c., or A +B,A B, A + 3 A + 5 B, &c., or 2 A + B, 2 A + 2B, 2A + 3B, &c., or 2A+ 3B, 2A+ 5B, 2A + 7 B, &c., or in some similar series. This is very fully exemplified in a large number of well known compounds-e. g., those of oxygen (0) and hydrogen (H), of which there are two, viz.: Water consists of 2 hydrogen and 1 oxygen, H2. Hydroxyl,, 2,, 2,, H202 or2 HO. Mercury and chlorine form two distinct compounds, viz.: Calomel, consisting of 200 parts of mercury and 35'5 parts of chlorine; Corrosive sublimate, consisting of 200 parts of mercury and 71 parts of chlorine; or one combining weight of mercury to one combining weight of chlorine, and one combining weight of mercury to two combining weights of chlorine. The most in LAWS OF CHEMICAL COMBINATION. 29 structive example of this rule is afforded by the series of compounds formed by nitrogen and oxygen. They are five in number, and the oxygen proceeds with marked regularity. The analysis of 100 parts of each gives the following results:Nitrogen. Oxygen. Nitrogen. Oxygen. Symbol. Nitrous Oxide,...... 63-64 36 36::28: 16 20 Nitric Oxide,........ 46-67 53-33::28: 32 N202 Nitrous Anhydride, 36-85 63-15:2: 8 N, 2O Nitric Peroxide,.... 30-44 69'56 28: 64 N204 Nitric Anhydride,. 25-93 74'07::28: 80 N205 Thus it will be seen that, while the proportion of nitrogen remains constant, being 28, or twice its comr bining weight 14, that of oxygen increases regularly, being 1, 2, 3, 4, and 5 times its combining weight 16. In most cases, the proportion is not always so simple, two parts of one element uniting with 3, 5, or 7 parts of another. This important law was first clearly established by Dalton, and has been made by him the foundation of his atomic theory, which we have yet to consider. 22. Law 3.-The third law of chemical combination is usually known as the law of equivalent proportions. It is sometimes called the law of combining proportions of elements. It may be thus stated, " Each elementary substance, in combining with other elements, or in displacing others from their combinations, does so in a fixed proportion, which may be expressed numerically." This law may be also expressed in another way, thus -"If a body, A, unite with certain proportions by weight of other bodies, B, C, and D, those proportions, or multiples, or sub-multiples of them, will represent also 30 INORGANIC CItE3IISTRY. the proportions in which B, C, and D will unite among themselves, or with any other bodies, E, G, HG, &c." It is the full consideration of this law which has en. abled us to determine the " combining or atomic weights" given in the first chapter. We are here met with a difficulty in distinguishing between " combining or atomic weight" and equivalent,-a distinction, which we shall not fully be able to understand until we have discussed the doctrine of equivalence or atomicity. The meaning of this equivalence will be seen on comparing the series of chlorides, as follows:lydrochlric of hCd,or I is composed of 35'5 parts chlorine, and 1 part hydrogen. Chloride of hydrogen, Chloride of zinc,......,, 35 35 35,, zinc. Chloride of silver,....., 35'5, 108, silver. Chloride of copper,....,, 35'5, 3175,, copper. Chloride of mercury,.,, 355,, 100,, mercury. So that, in power of combination with the same quantity, 35-5 parts of chlorine, 1 of hydrogen, 32'5 of zinc, 108 of silver, 31'75 of copper, and 100 of mercury, seem to be equal, and might be regarded as equivalents. But mercury and copper both form other chlorides, containing twice the amount of metal above given, viz., 200 parts of mercury, or 63-5 parts of copper, will each combine with 35'5 parts of chlorine. These two metals then would seem to have each two equivalents. Which is the true one, and which is to be taken as the combining or atomic weight? In all such ambiguous cases the true combining weight is found by a comparison of the combinations of the elements in question with other elements, and notably with oxygen; in the cases in point mercury is never found combining with oxygen in a lower ratio than 200 to 16, and copper in a lower ratio than 63-5 to 16. The numbers then, 200 and 63-5, are taken as the combining weights of mercury and copper respectively. 23. Law 4. —The fourth law of chemical combination ATOMIC THEORY. 31 may be stated thus-" The combining weight of a chemical compound is the sum of the combining weights of its components." ThusHydrochloric acid (which is made up of one part of hydrogen, and one part of chlorine), has for its combining weight 36'5, which is obtained as follows:1 part of hydrogen,..................... 1 1,, chlorine,..................... 355 Hydrochloric acid,.................. = 36'5 So sulphuric acid (which is made up of 2 parts of hydrogen, 1 part of sulphur, and 4 parts of oxygen,) has for its combining weight 98, obtained as follows:2 parts of hydrogen,.................... 2 1,, sul hu..................... 32 4,, oxygen, I.................... 64 Sulphuric acid,....................... 98 And in like manner for all other compounds. This law, which necessarily follows from the other laws, and from the fact that in chemical combination no loss of weight takes place, is nevertheless very important in a practical point of view, since by it we are able to regulate exactly the amount of any chemical compound we must employ in order to produce a given chemical effect, without loss or waste of material. 24. Atomic Theory.-The atomic theory, for which we are indebted to Dalton, presupposes matter to be composed of ultimate undivisiblo particles or atoms (from a, not; r-.yvt, I cut), which unite together in various proportions; that these atoms are in the same element, exactly similar in size, weight, and every other property; that the atoms of any one element differ from those of all other elements in weight and chemical properties; and when union takes place, it must of necessity take place betw een atom and atom, or between a definite number of atoms of both elements. It would follow, then, that granting the 32 INORGANIC CHEMISTRY. existence of such atoms, and that the atoms of any one element must be equal in weight, while the atoms of different elements would differ in weight, chemical combination, if it did take place, would do so in certain well marked definite proportions by weight, viz., the relative weights of the different atoms, or in some multiples of those weights. All observation and experiment show us that chemical combination does so take place. As we cannot explain the facts of chemical combination by any other hypothesis, these facts become a strong " a priori" proof of the truth of the atomic theory. Still, it can never be more than theory, since it would be impossible that we should ever succeed in isolating an atom, and thus obtain direct proof; while, mentally, we cannot conceive of any particle, however small, but that we can also conceive of its half, or any fraction of it; and mathematically, it is possible to demonstrate that space, and therefore matter, which occupies space, is capable of infinite subdivision. Thus, let A, B, C, D be lines drawn parallel to each other; draw the oblique line FG, and from F on the indefinite right line CD C.a b C 6 D Fig. 7. take any number of equal parts, as F, a, b, c, d, &c. From any point E in the straight line AB draw lines connecting this point ATOMIC THEORY. 33 with a, b, c, d, &c., cutting the oblique line FG; then, as the number of points, a, b, c, d, on the line CD may be infinite, it follows that the line FG may be infinitely divided, by lines connecting such points to E. Matter has been actually divided to an extent that is positively inconceivable, although not inappreciable nor immeasurable, and yet we are not able to assert that we have arrived at the ultimate limit; we can only say that our physical means of division and measurement are for the present exhausted, e.g."In the ordinary process of making gold leaf, for example, the gold is hammered out so thin that 280,000 leaves would be required to make up the thickness of an inch, and a single grain of gold is hammered out until it covers a square seven inches in the side. Each square inch of this may be cut into 100 strips, and each strip into 100 pieces, each of which is distinctly visible to the unaided eye. A single grain of gold may thus, by mechanical means, be subdivided into 49 x 100 x 100 = 490,000 visible pieces. But this is not all; if attached to a piece of glass this gold leaf may be subdivided still further; 10,000 parallel lines may be ruled in the space of one single inch, so that a square inch of gold leaf, weighing - of a grain, may be cut into 10,000 times 10,000, or 100,000,000 pieces, or an entire grain into 4,900,000,000 fragments, each of which is visible by means of the microscope. Yet we are quite sure that we have not even approached the possible limits of subdivision, because, in coating silver wire, the covering of gold is far thinner than the gold leaf originally attached to it, since in drawing down the gilt wire the gold continues to become thinner and thinner each time, in proportion as the silver wire itself is reduced in thickness." " When a substance is dissolved in any liquid, the subdivision is carried still further, and the particles are rendered so minute as to escape our eyesight, even when aided by the most powerful magnifiers."-Miller's Chemical Physics, page 5. It may be, and probably always will be, impossible to actually demonstrate the physical existence of an atom; but as a celebrated modern chemist has remarked, " that whether matter be atomic or not, thus much is certain, that granting it to be atomic, it would appear as it now does." The late Professor Faraday sums it up in these words-" Seeing that all marked cases of chemical combination can be demonstrated always to take place in definite proportion, and that, by inference, a similar proportionality may be supposed to extend to less marked cases,-seeing that these definite proportions of bodies entering into combination are mutually proportional amongst themselves, it follows that such definite immutability, such proportionality, should most rationally be considered as indicating a ponderable ratio between combining elements j and 10 E. C 34 INORGANIC CHEMISTRY. that the ratio never changing would seem to be indicative of elementary ponderable molecules of determinate relative weight, unchanging, indivisible, qualities which will be recognised as fulfilling the definition of an atom." Granting, then, (1.) The existence of atoms; (2.) That the atoms of the same element are absolutely identical in size, weight, and all other respects; (3.) That the atoms of one element differ from those of another element in weight and chemical properties; and (4.) That whenever combination takes place between two elements, it occurs between them atom to atom-Miller draws these three conclusions:" First, That the proportion in which combination occurs must, when the same compound is formed, always be definite, since that proportion is determined by the relative weights of the atoms of the combining elements, and the atom cannot be subdivided." "Second, That when the same elements unite in several proportions, these proportions must vary according to the terms of a simple series of multiples, since each atom of one element must unite with the other element in the ratio of one, of two, or of three atoms, or in some other ratio equally simple, inasmuch as the atom does not admit of subdivision." " Third, That combination must occur also in equivalent proportion, since the equivalent amounts of each element must be in the proportion either of the weights of their atoms, or of a simple multiple of those weights." The chemist then uses the term " atom," much as he uses that of " element," not as expressing an absolute fact, but as a convenient term to express what is observed to be the case according to our present knowledge. 25. Combining Volumes.-When bodies are capable of assuming the form of gas or vapour, a very simple relation exists between the volumes or bulks of those gases which combine togetner and the bulk of the gaseous compound formed by their union. The law is known as Gay Lussac's law of volumes. It is found that gases or vapours unite together by volume either in the proportion of equal bulks or in that of one volume to two volumes, or one to three volumes, or in some very rare cases in that of two to three. Thus equal volumes of hydrogen and chlorine unite together to form hydrochloric acid; two volumes of hydrogen unite with one volume of oxygen to VOLUME WEIGHTS. 35 form water; and three volumes of hydrogen unite with one volume of nitrogen to form ammonia. 26. Volume Weights.-This arises from the fact, that if equal quantities or volumes of the elements in the state of gas or vapour be taken, their weights will be found to be in the ratio of their atomic weights." Thus44 4 cubic inches of hydrogen weigh 1 grain. 44-4,,,, oxygen,, 16,, 44-4,,,, nitrogen,, 14 44'4,,,, chlorine,, 35'5,, and so on. Or putting it in French measure (see next chapter)11019 litres of hydrogen weigh 1 gramme. 11'19,, oxygen,, 16,, 11'19,, nitrogen,, 14, 11-19,, chlorine,, 355,, and so on. After union, the volume of the resulting compound, though frequently less than the combined volume of its constituents, bears, nevertheless, a simple relation to it. When gases combine together in equal volumes they generally undergo no change of volume; sometimes, however, the two volumes become condensed to one; in other cases the three volumes become condensed to two, as in the case of water, or even to one. In no case, however, do the combined gases occupy a larger space than they did when separate. In estimating the relation between the volume and weight of all gases and vapours, both simple and compound, reference must always be made to the temperature and pressure to which they are subjected. Heat has the property of expanding all things, but gases and vapours expand very largely for any increase of * An exception to this law obtains in the case of the vapours of phosphorus, arsenic, mercury, zinc, and some other less important elements. 36 INORGANIC CHEMISTRY. temperature. It has also been found, by accurate experiments, that gases expand regularly for every increase of temperature, the rate of expansion being -13 of their volume at zero or freezing point, for every increase of 1~ centigrade. Thus273 volumes or measures of air or gas at 0~ C. become 274,,,,,, 1~ C. 275,,,,, 2~ C. 273+x,,,,, C., and so on. The fraction -— 3 is represented by the decimal fraction 0-003665, and so1 volume of air or gas at 0~ C. becomes 1 003665 lo, 1~ C. 1 007330,,,, 2~ C. 1-010995,,,,, 30 C., and so on, the pressure in all cases remaining the same. But the volume which a given quantity of gas occupies at any temperature depends also on the pressure. If the pressure under which the gas exists be removed or lessened, the gas will immediately increase in size or volume; and if the pressure be increased, the volume of the gas will be diminished regularly. The law according to which this takes place was discovered by Boyle in England, and by Mariotte on the Continent, independently of each other, and known as the Law of Boyle and Mariotte. It may be thus enunciated-" Thbe temperature remaining the same, the volume which a gas occupies varies INVERSELY as the pressure to which it is subjected; or, the density of a gas is proportionate to its pressure." Thus1 volume or measure of air or gas under 1 pressure will become 2 vols.,, measures,, ~,, 3 vols.,, measures,, B,, Again1 vol. or measure of air or gas under 1 pressure will become i vol.,, measure,, 2,, vol.,, measure,, 3,, and so on, provided the temperature remains the same. VOLUME WEIGHTS. 37 If the temperature and tile pressure both vary, the volume of the gas will vary, directly as the temperature, and inversely as the pressure. The standard temperature and pressure at which the volumes of gases and vapours are recorded, are 62~ F., and barometer at 30 inches; or, in French measure, 0~ C., and barometer 760 m.m. (= 29'9 English inches). If the volume of a given quantity of a gas, at other than the normal temperature and pressure, be required, the corrections for each must be made separately, as in the following examples:1. 100 cubic inches of a gas are taken at 15~ C. What volume will they occupy if the temperature be raised to 20~ C. Now, since gases expand -3 of their volume at 0~ C. for each degree centigrade,.'. 273 vols. at 0~ C. = 288 = (273+ 15) vols. at 15~ 0. and 273 vols. at 0~ C. = 293 = (273 + 20) vols. at 20~ C. vol. at 15~ C. vol. at 16~ C. vol. at 00 C. vol. at 0~ C.'. 288: 100:: 273: x Here x = 94-792 cub. in. i.e., 100cubic inches of gas at 15 C. = 94 792 cub. in. at 0~. Againvol. at 0 C. vol. at 00 C. vol. at 20~ C. vol. at 20~ C. vol. at 10~ C. vol. at 0~ C. vol. at 20~ C. vol. at 100 C. And x = 101'7364 cub. in. Answer. i.e., You first reduce the given volume of the gas at the given temperature to its corresponding volume at 0~ C., and then by means of the fraction 2-, you can find its volume at the required temperature. 2. 100 cubic inches of a gas are taken when the barometer stands at 31 inches, what volume will it occupy if the barometer sink to 28 inches The observed volume is taken at 31 inches, while the required volume is to be at 28 inches, and as gases expand 38 INORGANIC CHEMISTRY. inversely as the pressure, the volume at 28 inches bar. -= of vol. at 31 inches bar. cub. inches. ~ of 100 = 3 of 25 = 5 _ =110'714285. This law of variation for temperature and pressure holds good for all gases, and for atmospheric air. The modification necessary for vapours, and for condensible gases when near their point of condensation, will bo explained in the Advanced Series. CHAPTER IV. French and English Systems of Weights and Measures —Cont version of English into French Weights and Measures-The Crith and its Uses. 27. THE accurate use of the balance, or in other words, the determination of the size and weight in which substances enter into combination, cannot be over-estimated in chemistry. By weight we understand the force with which gravity acts, and which at the same place is always constant. The selection of a standard of comparison for this force is purely arbitrary. In England we make use of a certain weight called a pound Avoirdupois; this we subdivide into7,000 parts, which we call grains, and we have further agreed to call 5,760 of these grains a pound Troy (the weight used for gold, silver, or precious stones). In chemistry it is customary to use Avoirdupois weight. The system of measures is connected with that of weight by the definition of a gallon as a measure which shall contain 10 lbs. of distilled water, at a temperature of 60~ F. WEIGHTS AND MEASURES. 39 (15-5 C.), and the barometer standing at 30 inches. A gallon of distilled water thus weighs 70,000 grains. These measures are, on the other hand, connected with those of length, by the determination that a gallon contains 277'276 cubic inches; consequently a cubic inch of water at 60~ F., barometer at 30 inches, weighs 252-4597 grains, or, in round numbers, 252 46 grains, or very nearly 2521 grains. The French use a decimal system of weights and measures, both of capacity and length. They adopt as the unit of their system the metre (frequently written and pronounced meter in English works); hence this system is generally known as the metric system. The metre (equal to 39 37079 inches, a little more than an English yard), was assumed to be the o, oo o th part of the earth's quadrant (from the equator to the poles, as determined by French geometricians)," and a bar of metal of this length was carefully prepared and deposited at Paris as a standard metre for future reference. The divisions of the metre are distinguished by the prefixes deci-, centi-, and milli-: so that a decimetre is Ij of a metre, a centimetre T-1-, and a millimetre TRUO of a metre. On the other hand, the multiples of the metre are distinguished by the prefixes deca-, hecto-, and kilo-, so that10 metres equal to 1 decametre. 100,,,, 1 hectometre. 1,000,,,, 1 kilometre. The measures of capacity are connected with those of length, by taking as the unit the contents of a cube whose side is equal to 1 decimetre (3'937 inches). This quantity is called a litre (equal to 1 7637 English pints), and has * Later and more accurate observations have demonstrated that this measurement of the earth's quadrant is in error to the extent of about 11 miles, so that the metre is very nearly, but not exactly,;,-a.-nrth part of the earth's circumference. This, however, does not interfere with its value as the unit of the metric system. 40 INORGANIC CtIEMISTRY. for its divisions and multiples the same prefixes as the metre, so thatrnT' litre equal to 1 millilitre or c~bic czntimetre, c.c, --,,,, 1 centilitre or 10,, c..,,,, 1 decilitre or 100, d.: 10 itres,, 1 decalitre. 100,,,, 1 hectolitre. 1,000,,,, 1 kilolitre. 10,000,,,, 1 myrioli(re. And, lastly, the system of weights is connected with both those of length and capacity, by assuming as the unit the weight of 1 cubic centimetre (c.c.) of distilled water, at a temperature of 4~ C. (39-2 F.) This is called a gramme (equal to 15 432 English grains), and is divided into tenths or decigranmmes, hundredths or centigrammes, and thousandths or milligrammes; while, in the same way as with the metre and litre, we have decagrammes, hectogrammes, kilogrammes, and myriagrammes, for 10, 100, 1,000, and 10,000 grammes respectively. The litre, as it contains 1,000 cubic centimetres of distilled water at 4~ C., is thus equal in weight to one kilogramme. The kilogramme is the commercial measure of weight in use in France. The decimal or metric system is found in many respects to be so convenient, that it is universally adopted in all scientific researches abroad, and is daily gaining ground among scientific men in this country. In this little work we shall give all weights and measures in the metric system, but shall add in brackets the nearest approximation in English value.< 28. Conversion of French System into English.-The following table will also materially assist in the conversion of French weights and measures into English:* Square measure is so little used in chemistry, that it has been omitted from this work. TIIM CRITH AND ITS USES. 41 FRENCIh. ENGLISH. Centigramme,....'15432 grains troy, about - grain. 4 Decigramme,...... 1 5432,,,, 1,, Gramme........... 15432,,,,15,, Decagramme,...... 15432,, nearly~ oz. Hectogramme,... 1543 2,, 31,, 1 Kilogramme,...... 15432,,,, 2 lbs. Millimetre.......... 03937 inches, about 31- inch. Centimetre,........ 3937,,,,,, Decimetre,......... 3-937,,,, - foot. Metre,................ 3937,, 31 feet. Decametre,......... 393-7,, nearly 11 yards. C Hectometre,....... 393707,,, 110,,. Kilometre,......... 39370-7,, about mile. Myriametre........ 393707-9,,,, 6 miles. Millilitre, or i Cubic centimetre, i'061 cubic inches, about cub. in. Litre................ 61027,,,, 1 pints. Decalitre,.......... 610-27,,,, 25 gallons. Hectolitre......... 61027,,,, 22,, 1 inch = about 2 centimetres. 1 yard = about - metre. 1 foot =,,3 decimetres. 1 mile =,, 1- kilometre. 1 cubic inch = about 16?- c.c. 1 cubic foot = about 28; litres. 1 gallon = about 44 litres. 1 grain............................ = about - gramme. 1 oz. troy,................... =,, 31 1 oz, avoirdupois,..............,, 28,, 1 lb.,,..............,, kilogramme. 1 cwt.,............ =,, 50, 29. The Crith and its Uses.-The crith (from KptLO1, a barleycorn), used figuratively to denote a small weight, is the term proposed by Dr. Hofmann, and since universally admitted, to indicate the absolute weight of 1 litre or cubic decimetre of hydrogen gas at the normal temperature and pressure, viz., temp. 0~ C., and pressure, barometer, 760 millimetres of mercury. Of this hydrogen unit Dr. Hofmann says, " The actual 42 INORGANIC CHEMISTnY. weight of this' cube of hydrogen, at the standard temperature and pressure mentioned, is'0896 gramme; a figure which I earnestly beg you to inscribe, as with a sharp graving tool, upon your memory. There is probably no figure in chemical science more important than this one to be borne in mind, and to be kept ever in readiness for use in calculation at a moment's notice. For this litre weight of hydrogen ='0896 gramme (I purposely repeat it) is the standard multiple or co-efficient, by means of which the weight of one litre of any other gas, simple or compound, is computed. Again, therefore, I say, do not let slip this figure,'0896 gramme." If we call the weight of 1 litre of hydrogen 1 crith, as the weight of equal volumes of gases will be in the proportion of their atomic weights, the weight of 1 litre of oxygen = 16 criths, of 1 litre of nitrogen = 14 criths, and of 1 litre of chlorine gas = 35-5 criths, and so on; while their absolute weight in grammes will be obtained as follows:I litre of oxygen 1 6criths= 16 x 0896 grammes =1'4336grammes. 1 nftrogenz=14,, =14x'0896, =1-2544, 1,, chlorine -35'5,, =355x'0896,, =31808,, So, in the case of compound gases, 1 vol. of hydrogen unites with 1 vol. of chlorine to form 2 vols. of hydrochloric acid (HC1) = 36-5 by weight. Hence 2 vols. of HC1 weighing 36'5, 1 volume must weigh 3' = 18'25; the weight therefore of 1 litre of hydrochloric acid gas, at the normal temperature and pressure, equal to 18-25 criths = 18-25 x -0896 grammes = 1-6351 grammes. So 2 vols. of hydrogen unite with 1 vol. of oxygen to form 2 vols. of water vapour, which weigh 18 units, therefore 1 vol. of water vapour must weigh 1-8 or 9 units, and consequently 1 litre of water vapour = 9 criths = 9 x'0896 grammes ='8064 grammes. In the same way, 2 vols. of hydrogen and 1 of sulphur unite together and form 2 volumes of hydrogen sul PRINCIPLES OE CHEMICAL NOMENCLATURE. 43 phide; now H S measures 2 volumes, and weighs 2 + 32 = 34; therefore 1 volume of H2S = 17 units, and consequently 1 litre hydrogen szlp7hide = 17 criths = 17 x OSOG grammes = 1-5232 grammes. Lastly, 3 vols. of hydrogen (= 3 criths) unite with 1 vol. of nitrogen (= 14 criths) to form 2 vols. of ammonia (I-SN), (= 17 criths); 1 vol. of H3N = 1 = 85 criths, and therefore1 litre of ammonia = 8'5 criths = 8'5 x'0896 grammes ='7616 grammes. Thus, the actual weight of a litre of any gas, simple or compound, at the normal standard of temperature and pressure, may be obtained by multiplying its atomic weight by'0896, the standard weight of a litre of!hydrogen. CHAPTER V. Principles of Chemical Nomenclature-Classification of Elements into Positive and Negative-Symbolic Notation-Chemical Formulae-Chemical Equations. 30. THE principle on which the system of chemical noiienclature is founded is, that in the case of the elements, the name shall give some idea of the nature, properties, and affinities of the substance; and in that of compounds, that it shall indicate the composition and constitution of the body to which it is applied. In the case of the elements, with some few exceptions, this object has been attained; but in that of compounds, it is difficult in a science like chemistry, where new discoveries are continually altering our views of the constitution of bodies already existing, or bringing fresh ones 44 INORGANIOA CHEMISTRY. to our knowledge, to devise a system of nomenclature which shall at the same time be sufficiently precise to express all existing views, and sufficiently elastic to embrace all new ones. On this account chemical nomenclature may be regarded as in a somewhat unsettled and unsatisfactory condition. In naming many salts, no less than four different usages prevail. Thus the salt, whose composition is expressed by the formula K2SO4, is known by the four following namesSulphate of potash. Sulphate of potassium. Dipotassic sulphate. Potassium sulphate. We shall perhaps better be able to explain the most general method on which the systematic names are constructed, if we first draw the distinction which is observed between the elements with respect to their electrical properties, or their division into basylous or electro-positive, and chlorous or electro-negative, elements. Chemical compounds are freely decomposed by electricity; when so decomposed, those elements which appear at the positive pole are called electro-negative, while those which appear at the negative pole are called electro-positive. The terms basylous and chlorous must be left without explanation for the present. It is somewhat difficult to arrange the elements in an electrical series, seeing no two observers exactly agree. Dr. Frankland gives the following eight elements as being negative or chlorous towards the remaining fifty-six elements, which are always more or less basylous:Fluorine. Oxygen. Chlorine. Sulphur. Bromine. Selenium Iodine. Tellurium. It must be borne in mind that the difference between the two classes, the electro-positive and electro-negative, is one of degree only. Mercury, for instance, is negative to sodium, and positive to iodine. The elements may be arranged in such a series that any one in combination is NOMENCLATURE OF COMPOUNDS. 45 electro-positive to any following, but electro-negative to all preceding ones. The following, table, taken from Ferguson's Electricity, page 122, agrees in the main with the order given by Berzelius. --- -~ ~ ~ ~ P4+ E )a'1 * e I,e S^1A d In this table oxygen is put as the most negative, but later researches have shown it to be almost certain that chlorine and its allied elements bromine, iodine, and fluorine, should stand at the negative end of the series. 31. Nomenclature of Compounds.-The simplest possible chemical compound is one formed by the union of two elements, and called a binary compound. The name of the positive element is placed first, with the adjective termination ic; and that of the negative element last, with the termination ide; thusMercury and chlorine produce mercuric chloride. Silver,, bromine,, argentic bromide. Potassium,, iodine,, potassic iodide. Iron,, sulphur,, ferric sulphide. Sodium,, oxygen,, sodic oxide. And so on. The same elements sometimes form two distinct compounds, as, for instance, iron unites with two different proportions of chlorine. To distinguish these, the name, "F errum,," of the iron (the positive element) is made to terminate in " ous," and "ic," respectively, viz., " ous " for the compound, which contains the least quantity of chlorine (the negative element), and "ic" for that which contains the larger quantity of chlorine; thusFerrouls chloride, FeCl,. Ferric Chloride, Fe, Cl'. * In cases where more than two compounds are formed * For explanation of these and succeeding symbols, see page 13. 46 INORGANIC CHEMISTRY. by the same elements (which is very rare), they are distinguished by the prefixes hypo- (beneath), and per- (hyper, above). Many of the binary compounds formed by oxycen have the property, when added to water, of acquiring acid characters. The term acid was originally applied to all substances which were soluble in water, had a distinctly acid or sour taste, and possessed the property of turning a vegetable blue colour red. Tincture of litmus, which is of a blue colour, is exceedingly sensitive to the action of an acid; and paper stained with this tincture (litmus paper) is the test which the chemist applies to detect the presence of an acid. All bodies which come under the above definition are still regarded as acids, but the term "acid" has now received a much more extended signification. 32. Frankland's Definition of an Acid.-It may be now defined to be a compound containing one or more atoms of hydrogen, which are capable of being displaced by a metal, either partially or entirely. Thus, hydrogen and chlorine unite together in equal volumes to form hydrochloric acid; if, now, the metal zinc be added to this, the acid is decomposed, zincic chloride or chloride of zinc is formed, and the hydrogen is set free. The change is represented by symbols, as follows2 HC1 + = Zn C12 + H2. Or in the case of acids containing oxygen, if the metal be presented in the form of a hydrate, the metal combines with the acid, and water is set at liberty; thus, if sodic hydrate be mixed with nitric acid, sodic nitrate is formed, and water set at liberty. The change may be thus symbolically representedIINO, + NaHtO = NaNOO + H-0. Nitric acid. Sodic hydrate. Sodic Nitrate. Water. FRANKLAND'S DEFINITION OF AN ACID. 47 All acids which contain oxygen" have their names formed by adding the termination "ic" to the name of the element which is combined with the oxygen, or else to an abbreviation of the name; thus, sulphur and oxygen form sulphuric acid; nitrogen and oxygen, nitric acid; phosphorus and oxygen, phosphoric acid; carbon and oxygen, carbonic acid, and so on. In the case of the element forming two acids with different proportions of oxygen, the one with the lowest proportion of oxygen is distinguished by the termination "ous," while that with the higher proportion receives the termination " ic." Thus, we have sulphurous acid, and sulphuric acid, nitrous and nitric acids, phosphorous and phosphoric acids, and so on. When the element forms more than two acids with oxygen, they are distinguished by the prefixes hypo- and per-; for example, oxygen and chlorine form four acids, as follows:Hypochlorous acid, C1HO. Chloric acid.......... C1HO3. Chlorous acid...... CIH02. Perchloric acid,.. C1IO4. The use of the prefix "per-" is generally limited to the compound containing the largest known proportion of oxygen. Some acids do not contain oxygen, but have sulphur instead; these have a prefix sulph- or sulpho-. Thus, a union of sulphur, arsenic, and hydrogen produces sulpharsenic acid; while one of sulphur, hydrogen, and tin produces sulphostannic acid. In these acids, as in the case of the oxygen acids, the less or greater proportions of sulphur present are denoted respectively by the terminations "ous" and "ic." When an acid is formed by the binary compound of hydrogen and another element, it takes the prefix hydror hydro-; in this case the terminations "c ic" and "ous" are not needed, since no element forms more than one acid with hydrogen. * Some acids which do not contain oxygen, as hydrochloric, hydrobroic, &c., nevertheless terminate in "ic." 48 INORGANIC CHEMISTRY. When a proportion of water is abstracted from any oxygen acid the residue is called an anhydride; thus12SO4 - HO = SO,. Sulphuric Acid. Water. Sulphuric Anhydride. 2N03H - HO = N205. Nitric Acid. Water. Nitric Anhydride. 33. Base.-Other binary and ternary compounds which never become acids, but which under all circumstances combine with the acids, and either neutralize them partially or entirely, are called bases. 34. Alkali.-Those bases which neutralize acids entirely are called alkalies. The term alkali is of Arabic origin (al, the; kali, plant); and was given in the first instance to sodic carbonate, which was obtained from the ashes of plants. It is now extended to a large class of substances, which, like scdic carbonic, are soluble in water, possess an acrid, nauseous taste, restore the blue colour to vegetable infusions which have been turned red by an acid, and turn many vegetable blues green, as for instance, the solutions of blue cabbage or of litmus. Alkalies also turn vegetable yellows, as those of rhubarb or turmeric, brown; but this test is not so delicate as that of its power of neutralizing an acid by restoring the blue colour to litmus paper which has been feebly reddened by an acid. The bases then may be divided into two classes-First, The oxides of metals; Second, Compounds of metals with a certain substance called hydroxyl (HO20,); these compounds are called hydrates. Some of these oxides and hydrates possess the power of entirely neutralizing or destroying the characters of the acids; these are called alkalies. To the latter class must be added ammonia (HN), which, though neither oxide nor hydrate, forms nevertheless a powerful base and alkali; it is a type of a numerous class of bodies met with in organic chemistry. The first class of bases, the' oxides,' are named strictly in accordance with the law given for the naming of binary ALKALI-SALTS. 49 compounds, as baric oxide, nagnesic oxide, and so on. When two oxides are formed, they are distinguished as before by the terminations " ous" and "ic." WVhen more than two oxides are formed, the number of atoms of oxygen to those of metal are signified by prefixes, as di-, tri-, tetra-; or in some cases the first oxide is called the monoxide; the second, the binoxide. In all cases the highest compound in a series often receives the prefix per-. When the elements combine together in the proportion of two atoms of the one to three atoms of the other, the prefix " sesqui-" (one and a half) is employed, as sesquioxide of iron, (Fe,O). The oxides of the following metals, whose names end in "umn" or " ium," are also known commonly by the following names:MIETALS — OXIDESPotassium.................................Potassa. Calcium,...................................Lime. Strontium,.................................Strontia. Barium,.........Baryta. Aluminium,................................Alumina. Magnesium,...................Magnesia. Glucinum................................. Glucina. Zirconium,........................... Zirconia. The bases of the second class or hydrates have simply the name of the metal or positive element with the termination " ous" or "ic" before the name hydrate formed from hydroxyl, e.g. Potassic hydrate......................... KHO. Sodic hydrate,.................. NaTlO. Zincic hydrate,..................................... Zn2HO. and so on. 35. Salts.-When an acid and a base-unite together a salt is produced. If the acid contained sulphur instead of oxygen, it is called a sulphosalt. If the acid contained neither sulphur nor oxygen, it is called a haloid salt (aXr, sea-salt); but if the acid be one containing oxygen it is a salt proper. 10 E. D 50 INORGANIC CHE2IISTRY. The nomenclature of the salts is exceedingly simple: those which are formed from acids terminating in " ous" receive a termination "ite"; while those formed by an acid ending in "ic" are made to terminate in "ate." Thus, a salt formed by sulphurous or nitrous acids, would be named a sulphite or nitrite; while those formed by sulphuric or nitric acid, would receive the name of a sulphate or nitrate. Any prefixes added to the acid would also be carried on to the salt: thus, a salt formed by hyposulphurous acid would be called a hyposulphite; while one formed by perchloric acid, would be called a verchlorate, and so on. 36. Symbolic Notation.-It has been already remarked that chemists, for the sake of convenience, have adopted a. principle of notation by symbols. It is a kind of shorthand, which greatly abridges the labour of description, and enables the changes and reactions that take place to be briefly and clearly represented, even when they are of a most complicated character. For the elements, the initial letter of their Latin name is made use of; and, in the case of two or more elements commencing with the same letter, the single initial is reserved for the earliest discovered or most important element; the others being distinguished by the addition of a small letter to the initial one. Further, these symbols represent not only the element, but one atom or combining proportion of the element. When more than one atom or proportion of the element is intended to be represented, it is done either by writing the number before the symbol of the element; or, hlow almost universally, by writing a small figure to the right of the symbol, and below the line. Thus, H would stand for one atom of hydrogen; 2H, or, more correctly, I12, for two atoms; H3, for three atoms, and so on. 37. Chemical Formulm.-When a compound body is intended to be represented, the symbols of its constituent elements are simply placed in juxtaposition. Thus, HICt is the symbol for hydrochloric acid; H20 is the symbol for water; AgO for argentic oxide; H2SO0 for sulphuric CHEMICAL FORMULA. 51 acid. Such a group of two or more symbols is called a chemical formula. We may then define a chemicat formzula to be "the expression, by symbols and numbers, of the composition of a chemical compound." In the ordinary symbolic language, the symbol of the most electro-positive element is placed first in the formula. Thus, water is written H20, not OH12; ammonia is HN, not NH,, and so on. When a comma is used to separate the members of a formula, these members are represented as united chemically, and a more intimate union is supposed to exist than when the members are separated by a period. A large figure placed before a symbol multiplies every symbol and figure up to the next comma or + sign; e.g. 3BaN,06 indicates Ba3N608O, or three parts of nitrate of baryta. But nitrate of baryta may also be written Ba,2NO,, indicating that one atom or proportion of barium is united with two atoms or proportions of NOs, in which case, to express three atoms of the salt, a bracket must be employed. Thus, 3(Ba,2lN0), as otherwise, on account of the comma, the 3 would have multiplied only the Ba, and not the 2fv03. Brackets are not now much employed, but, when they are, the effect of a number before them is to multiply all the terms within them. The + sign should never be used to connect together the constituents of the same compound, but only when two different bodies are added to or mixed with each other. The - sign indicates abstraction, but it is seldom employed. The formula for sulphate of zinc is sometimes written ZnSO4, and sometimes ZnO,SO,. In the first, it is merely intended to represent the actual composition of the salt, without in any way asserting how its component atoms are linked together. Such a formula is called an empirical formula, and may be regarded as a simple statement of fact involving no theory whatever. In the second case, 52 INORGANIC CHEMISTRY. the formula asserts that one atom of oxygen is united with one atom of zinc to form oxide of zinc, which again unites itself to one part of sulphuric anhydride (SO,) to form sulphate of oxide of zinc, or more briefly, sulphate of zinc, or zincic sulphate. Such a formula is called a rational formula, because it attempts to account for the way in which the constituent atoms are grouped together. Such a formula may be, and probably is, true in the majority of cases; but it must ever be borne in mind that it is only theory. 38. Chemical Equations.-The changes or reactions which take p'lace under the influence of chemical action may be represented in two ways-either by means of a diagram, or by an equation. If we mix together solutions of common salt (sodic chloride) and argentic nitrate in proper proportions (sodic chloride, NaCI = 58'5; argentic nitrate, AglVO3 = 170), the sodiumn and the silver change places, and sodium nitrate and argentic chloride are formed. This double decomposition, as it is called, may be represented by a diagram, as follows58. Sodic f 355 Chlorine 11345 -Choride 58'5 {Chloride 230 Sodium {Chjoidei {23'0 Sodium / {'5{ Chloride. 170'0 Argentic 14-0 Nitrogen 85 Sdi t 48e 0 Oxygen Nir 85ate. N 108'0 Silver This change may be, however, better and more simply represented by means of an equation, in which the substances as they exist before the reaction are placed on the left hand side, while those which are formed by the reaction are on the right. ThusNaCl + AgNO3 = AgCl + NaNO,. Sodic chloride. Argentic nitrate. Argentic chloride. Sodic nitrate. Or Zn. + Cl2 ZnC12. Zinc. Chlorine. Zincic chloride. 2HC1 + Na, = 2NaC1 + Io. Ilydrocblorio acid. Sodium, Sodic chloride. Hydrogen. ATOMICITY OF ELEMENTS. 53 The sign = in a chemical equation does not mean "equal to," but is to be regarded rather in the sense of "yields" or "produces," or "is converted into." ThusZn + H2SO4 = ZnSO4 + H2. Zinc. Sulphuricacid produces Zincic sulphate. IIydrogen. CHAPTER VI.J Atomicity of Elements-Classification according to AtomicityGraphic Notation-Simple and Compound Radicals-Definition of a Compound Radical. 39. THE combining or atomic weights of the elements were formerly called equivalent numbers, as these proportions were considered equal to each other in chemical combination; but more accurate knowledge shows us to have beenin error. We now find that the atoms of the different elements are by no means equal in chemical combination. For instance, sulphuric acid has the following formula, H2 SO4; if we now put to it sodium or potassium, we find that for every atom or equivalent of metal taken up, one atom or equivalent of hydrogen is set free, as shown by the following equations:(1.) H2SO4 + K = KHSO4 + H. (2.) H2S04 + Na = NaHSO, + H. While if zinc or iron be added to the sulphuric acid, for every atom or equivalent of metal taken up two atoms of hydrogen are set free, as follows:(3.) H2SO + Zn = ZnSO4 + H,. (4.) H2SO, + Fe = FeSO, + H2. * The whole of this chapter is, by Professor Frankland's kind permission, taken from his Lecture Notes for Chemical Students, in many parts the passages being copied verbatim. 54 INORGANIC CHEMISTRY. So that, while the atoms of K and Na are capable of replacing only one atom of H in a chemical combination, those of Zn and Fe can replace two atoms of H; clearly, then, the atoms of K or Na are not equivalent to either those of Zn or Fe. If we regard the following series of compounds as typical, viz.:Hydrochloric Acid,..........1 11................ W ater,..................................................... H 0. Ammonia................................................. N. M arsh Gas,............................................... H C. We shall see that atoms of C1, O, N, and C require, or are capable of combiining with, 1, 2, 3, and 4 atoms of H respectively, or, in other words, that oxygen has twice, nitrogen three times, and carbon four times, the atom fixing power, as far as hydrogen is concerned, that chlorine has. Again, while hydrogen and chlorine combine together atom to atom, as in hydrochloric acid (HC1), other elements are capable of taking up different numbers of atoms of chlorine, as in the following series:Hydrochloric Acid,................................. HC1 Baric Chloride,.................................... BaCI,. Auric,,................................. AuCl,, Platinic,,.................................... PtC. Antimonic,,................................... bCl. Thus, one atom of barium, combines with two atoms of chlorine, and is therefore equal to (in combining power) two atoms of hydrogen; in like manner one atom of gold may be regarded as equal to three atoms of hydrogen, one ofplatinum to four atoms, and one of antimony to five atoms of hydrogen. From this we see clearly that the equivalents of elements are not necessarily their atomic weights. 40. Definition of Atomicity.-By equivalence or quantivalence or atomicity of an element, we mean the number DEFINITION OF ATOMIICITY. 55 of atoms of hydrogen (and therefore also of chlorine) which it is capable of replacing in a compound. 41. Monads.-Those elements which, in combination, only replace one atom of hydrogen or chlorine are called monads, monequivalent, or univalent elements. The chief are, Na, K, Ag, Br, I, F, &c. The compounds they form are, NaCl (sodic chloride), KCl (potassic chloride), AgCl (argentic chloride), HIBr (hydrobromic acid), HI (Hydriodic acid. 42. Dyads.-Elements which, like oxygen, barium, calcium, &c., are capable of replacing two atoms of hydrogen in combination, are called dyads, diequivalent or divalent elements. 43. Triads.-Those which, like gold and boron, can replace three atoms of hydrogen, are called triads, triequivalent or trivalent elements. 44. Tetrads.-Tetrads, tetriquivalent or tetravalent elements, are those which, like carbon, tin, silicon, platinum, lead, &c., can replace four atoms of hydrogen. 45. Pentads.-Pentads, pentequivalent or pentavalent elements, are those which, like nitrogen, phosphorus, &c., can replace five atoms of hydrogen. 46. Hexads.-Hexads, hexequivalent or lexavalent elements are those which replace six atoms of hydrogen, e.g. sulphur, iron, cobalt, nickel, &c. The following classification of the atomicity of elements is taken from Dr. Frankland's Lecture Notes for Chemical Students, page 32. It is not quite in accordance with that given by the late Dr. Miller or by other authors; but it is, we think, the one most easily understood and proved. MONADS. DYADS. TRIADS. TETRADS. PENTAD. EXADS. 1st Section. 1st Section. 1st Section. 1st Section. 1st Section. st Section. W HYDROGEN. Oxygen. BORON. CARBON. NITROGEN. Sulphur. ^ —----— dw~~ - ----- SILICON. PHOSPHORUS. Selenium. TIN. ARSENIC. Tellurium. 2nd Section. 2nd Section. 2nd Section. TINARSENIC. Tellurium. Fluorine. BARIUM. GOLD. TITANIUM. T Oc~ TITANIUM. ANTIMONY. hlorine. BTRONIUM. GDBISMUTH. 2nd Section. Chlorine. STRONTIUM. It Bromine. CALCIUM. 2nd Section. TUNGSTEN. O Iodine. MAGNESIUM. THORINUM. VANADIUM. ------- ZINC. NIOBIUM. MOLYBDENUM. I' 3rd Section. TANTALUM. CAeSIUM. 3rd Section. ZIRNIUM.3rd Secton. RUBIDIUM. DIDYMIUM. ALUMINIUOSMIUM. CD POTASSIUM. LANTHANUM. IRIDIUM.:. SODIUM. YTTRIUM. 3rd Section. RUTHENIUM. o LITHIUM. GLUCINUM. PLATINUM. RHODIUM. M. —------- --------— PALLADIUM. 4th Section. 4th Section. 4th Section. THALLIUM. CADMIUM. 4th Section. CHROMIUM. O SILVER. MERCURY. LEAD. MANGANESE. COPPER. IRON. COBALT. 0CD C OB INICKEL. s0-I~~CD.~~~ I 1 ( ( ) I ~~URANIUM. g______________ ____ ___CEERIUM. In the above table the non-metals are printed in thick type, and the metals are put in ordinary type, whilst the rg positive or basylous elements are printed in capitals, and the negative or chlorous elements in small letters. GRAPHIC NOTATION. 57 is marked by accents or equivalence marks, and Roman numerals placed above and to the right of the symbol; thus, Hi, OWi, Biii, Civ, Nv, Svi 47. Graphic Notation.-In the graphic notation the elements are represented by a ball having the symbol of the element inside of it, and having as many rods or pegs proceeding from it as mark its atomicity; thus hydrogen, (; oxygen, —; boron,'; carbon, -)-; nitrogen, AN,; sulphur, These rods or pegs are regarded as forming points of attachment for other bonds and pegs of other atoms either of the same or different elements. Thus, an atom of hydrogen cannot exist independently, as (, there being a bond unsatisfied; but two atoms of hydrogen, forming a molecule,s can exist, the bonds of each mutually satisfying each other, thus, (~-<-. It is yet a disputed point whether the bonds of the same atom can satisfy each other; thus, whether the atom of oxygenancan exist alone in this manner, ), or whether we must regard it as a molecule, thus, (-==. Dr. Frankland seems to regard it as possible that the bonds can satisfy each other; and in a large number of compounds we can explain the facts in no other way than that they do satisfy each other. Hydrochloric acid may be thus graphically represented, ~-@. Water, thus ~ —@. * A molecule is regarded as the smallest portion of an element or compound which is capable of a separate chemical existence. It may consist of two or more atoms, 5 8 INORGANIC CHEMISTRY. lfagnesic oxide, thus, (, (both elements being dyads). Ammonia, thus, (i; and so on. The element nitrogen appears as a triad in ammonia, 1I7H Ni aud as a pentad in ammonic chloride, ~) NVcITl. C Again, slphz1ur appears asDyad in Hydric sulphide, SEiH ) 2 - Tetrad in Sulphurous anhydride, SiO2 (. =~ Hexad in Sulphuric anh.ydride, 5ViO It is then a law, to which there are no real exceptions, (the apparent ones admit of a simple explanation), that though the equivalence of an element may vary, it does so always by the addition or subtraction of an even number-i.e., a pentad element may become a triad, or even a monad, but can never, under any circumstances, become a dyad, tetrad, or hexad; so again, a hexad may in some combinations appear as a tetrad or a dyad, as in the cases of sulphur quoted above, but can never be a monad, triad, or pentad. In other words, an element having an even equivalence cannot ever become oddequivalent; nor can an element which has odd equivalence ever possess even equivalence. 48. Perissads and Artiads.-On this accountDr. Odling ABSOLUTE, ACTIVE, AND, LATENT ATOMICITY. 59 has proposed to divide the elements into two classes, "perissads" and " artiads," (from rEpocrorv, uneven, odd; and apTrio, even), or perissequivalent, and artiequivalent elements. Dr. Frankland's explanation of this diversity of equivalence of the same element is this-" that one or more pairs of bonds belonging to one atom of the same element can unite, and having saturated each other, become, as it were, latent." Thus the pentad nitrogen becomes a triad when one pair of its bonds becomes latent; and a monad when two pairs, by combination with each other, are rendered latent. These conditions are represented graphically, thusPentad. Triad. Monad. And so in the case of sulphurHexad. Tetrad. Dyad. 49. Absolute, Active, and Latent Atomicity.-Dr. Frankland, on this hypothesis, regards all the bonds which an element possesses as its absolute atomicity; those which are concerned in linking it with the other elements of a compound as its active atomicity; and the number of bonds which are united together as its latent atomicity. So that the sum of its latent and active atomicities must always be equal to its absolute atomicity. From these facts on equivalence we deduce two important conclusions, viz.:1. That the sum of the bonds of a molecule must always be an even number, since the atoms are bound together by the bonds which constitute the equivalence of their component atoms, and that no bond can be left disengaged or unsatisfied. So that a formula which possesses an uneven number of bonds or units of chemical affinity, cannot possibly represent a molecule. 60 INORGANIC CHEMISTRY. 2. No portion of a molecule can be removed without leaving one or more of the bonds of the molecule unsatisfied, the substances left are therefore incapable of a separate existence, e. g., a molecule of marsh gas isSymbolic. Graphic. CiVH, ( -— H); if we take away one atom of hydrogen, we have left a molecule of Meth y, CivilH,, M which has one bond unsatisfied; and is, therefore, ready to unite with any monad atom, or with any molecule simple or compound which has one unsatisfied bond. Now, if we take from this another atom of hydrogen we leave a molecule of Jletl7ylene, CiVH]2 C ~ which, from its having two bonds unsatisfied, may be regarded as a dyad compound molecule; if, further, from this molecule of methylene we abstract another atom of hydrogen we shall have a molecule of Fornyl, CivH which may be viewed as a triad compound molecule; and, if we still further abstract this remaining atom of hydrogen, we shall leave the tetrad elementary atom of carbon Ci -(-, having four bonds unsatisfied. Every atom or molecule which, from its having bonds unsatisfied, is ready to enter into combination, is called a DEFINITION OF COMPOUND RADICAL. 61 radical; if it is elementary or simple in its nature, it is called a simple radical; if it is compound, it is called a compound radical. 50. Definition of Compound Radical.-When two or more simple radicals (i.e., elements) combine, they either form a compound radical or salt. They form a compound radical if the substance produced is capable of entering further into chemical composition or combinations, without itself suffering decomposition. ThusPotassium. Hydroxyl. K2 + 20"H O"KH + O"KH. In the above series of combinations of C and H, methyl, methylene, andformyl, are all of them compound radicals, and are respectively regarded as monad, dyad, and triad, according to the number of bonds of attachment which remain unsatisfied. All compound radicals have their equivalence marked on the same principle The three in question may be written thus-methyl (CH3 ); methylene (CH,)"; formnyl (CH)"' Sometimes it is necessaryto givenames to compound radicals, and to substitute for their formula a single symbol, e.g., the radical mzethyl C'IH, is represented by symbol Me; so the radical O"H is called hydroxyl, and is represented by symbol Ho. The following are the names and formulae of the chief inorganic compound radicals recognized by chemists:Abbreviated Molecular Atomic atomic formulae. formula. formule. Hydroxyl..................... (HO)2 HO Ho. Hydrosulphyl.............. (HS)2 HS lis. Ammonium,................. (NH4), NH, Am. Ammonoxyl................. (NH4O)2 NH,O Arno. Amidogen,................... (NH2)2 NH Ad. * It is customary to omit the equivalence marks to monad radicals, both simple and compound. 62 INORGANIC CHEMISTRY. Besides these, certain compounds which metals form with oxygen are regarded as compound radicals, asAbbreviated Molecular Atomic atomic formul,. formula. formula. Potassoxyl...... (KO)2 KO Ko onad. Sodoxyl,........ (NaO)2 NaO Nao monad 0 Zincoxyl,......... (ZnO2) Zn' Zno". (0O Cuproxyl,......... (CuO2) Cu Cuo". And so on. The essential character of these last compound radicals is that the whole of the oxygen they contain is united with the metal by one bond only of each oxygen atom, as seen in the following graphic formula:Hydroxyl,........................... - Potassoxyl,....................... Zincoxyl,............................ - The metal thus becomes linked to other elements by these dyad atoms of oxygen. The functions of such compound radicals will be sufficiently evident from the following examples of compounds into which they enter, and in which their position is marked by dotted lines:Nitric Acid, HNO3 o —-- ~:........)...... PotSsic Sulphate, I2SO ~ ~()-~, 1,_, __. __:,,, ____0, _ USE OF TI-ICFI TYPE, 03 Baric Nitrate, Ba, ~ON0, C) -- - @ -__.- "*-" —-_________XXw il!1 Zincic Sulphate, ZnSOW -.........-.; i It is not necessary to name all these metallic compound radicals. The only point of importance is their abbreviated notation in which the small letter o is attached to symbol of the metal-the atomicity of the radical being marked in the usual manner. 51. Use of Thick Type.-The system of graphic formulse attempts to show how each unit of force of each of the atoms is expended; but the same thing can be shown by means of symbols. For this purpose the first symbol of a formula should be that of the element which is directly united with all the active bonds of the other elements or compound radicals which follow it upon the same line: thus, the'formula SO Ho (sulphuric acid) signifies that the hexad atom of sulphur is combined with the four bonds of the two atoms of oxygen, and also with the two bonds of the two atoms of hydroxyl.. When the element which is thus placed first has more than one bond, it will be printed in thick type, and, as a rule, the element having the greatest number of bonds will occupy this position. Thus* Such a formula is called a rationlalformula, as it attempts to account for the way in which the elements are united together. When, however, a formula simply gives the composition of a substance without regard to the arrangement of its components, it is called an empiricalformula. 64 INORGANIC CHEMISTRY. Empirical Formulae. Rational Formule. W ater,..................... I 0 OH2. Sulphuric acid,......... H2SO4 SO2Ho,. Nitric acid.............. HNO,3 02Ho. Microcosmic salt....... NaH4NHPO4 POHoAmoNao. 52. Use of Bracket.-These atoms in thick type form the central or governing atoms around which the others are grouped, to indicate which a bracket is used, as in the following three examples:1. 2. 3. CH3,. (CH,. COO. CH,. O. Ba. CH,. COO. " The formunla No. 1 signifies that two atoms of carbon "are directly united with each other; No. 2, that two "atoms of carbon are linked, as it were, together by an " atom of oxygen, the latter being united to both carbon "atoms; whilst in like manner No. 3 expresses the fact "that one atom of oxygen in the formula of the upper line "is linked to another atom of oxygen in the formula of the "lower line by an atom of barium." So, again, ferric chloride, the empirical formula for which is Fe2Cl6, can be represented by the thick letter symbols in two ways, thus - Graphic Ferric chloride,''Fe"C or "'Fe"'Cls indicating that the two atoms of iron (each being hexad) are linked to each other by three of their bonds, leaving their other three bonds available for their union, each with three atoms of chlorine. The equivalence marks are not inserted with the monad elements; nor in the case of oxygen, which is invariably dyad; nor with carbon, unless its equivalence USE OF BRACKET. 65 be reduced to ". The marks are also omitted in cases where there can be no difficulty in assigning the equivalence of the elements. It will be thus seen that this method of symbolic notation, by means of equivalence marks and thick letters, expresses exactly the same thing as the graphic notation, which is somewhat cumbrous for general use; but still the graphic system, especially if supplemented by Hofmann's glyptic method, is of incalculable use in the lecture theatre, in bringing vividly before a class, and making easy of comprehension, the changes that take place in even the most simple reactions. The objection made to the graphic and glyptic, and also to the symbolic formulae of Dr. Frankland, viz., that it is a purely theoretical attempt to give a picture of the physical arrangement of atoms, is, I think, repudiated by every teacher, who has made a fair and impartial trial of the methods. In the remainder of this little work, when treating of the elements, their preparation, properties, and combinations, I shall express all reactions in equations, using Dr. Frankland's method of symbolic notation; but, for the convenience of those who do not understand or approve of that method, and for the sake of comparison with the many standard works which do not use it, such as those of Miller, Roscoe, Fownes, Galloway, &c., I shall add, in brackets thus [ ], the equation in the old method of notation. I shall also, wherever I think it useful, give the graphic formulae. 10 E. E Go INORGANIO CHEMISTRY. CHAPTER VII. Hydrogen-its History-Distribution and Natural History-Pre. paration-Properties- Combinations. 53. Hydrogen.-Symbol HI.-Atomic weight = 1. Atomic volume, 7J. Density = 1. Specific gravity = 0-0692. 1 litre weighs 1 crith. Molecular weight, 2. Molecular volume, ~~l. Atomicity,', being the standard of comparison. 54. History.-The element chydrogenwas first mentioned in the sixteenth century by Paracelsus, but very little was known of it in any way. According to Faraday, it seems to have been regarded in the 16th century as synonymous with the "phlogiston" of Beecher and Stabil, from its burning so eagerly in the air. It was afterwards called inflammable air, for the same reason, and was confounded with several of its compounds. In 1766, it was first obtained in a pure state, and its properties thoroughly examined; and soon afterwards it was named hydrogen (USwp, water; ysEVLv, to generate) by Lavoisier, from its being found that its combination with oxygen produced water. 55. Distribution and Natural History.-l-ydrogen is very rarely found free in nature, but exists very largely in combination, both in the inorganic and organic kingdoms. In the former it is found as a constituent of various acids in combination, as the hydrochloric, hydrobromic, hydriodic, and hydrofluoric acids. It is a constituent of certain liquids, as water, naphtha, petroleum; and also of certain solids, as in the salts of ammonia. In the organic kingdom, it is found largely entering into the composition of both animals and vegetables, in the forms of water (HO2) and ammonia (HN). 56. Preparation.-It is most generally obtained from water, by the action of substances on the water, which are PREPARATION OF HYDROGEN. 67 capable of removing oxygen from it, and setting free the hydrogen. (1.) Thus, if pieces of the following metals-potassium, sodium, lithium, barium, strontium, calcium, magnesium,-are added to water, they will decompose it, and set free the whole, or a portion of the hydrogen. The first three-K, Na, and Li-being monads, displace only one part of the hydrogen contained in water, — the reaction which takes place being represented by the following equation:20H, + Na, 2 ONaH + H, Water. Sodium, Sodio hydrate. Hydrogen. The last four-Ba, Sr, Ca, and Mg-are dyads, and therefore displace two proportions of hydrogen, as shown in the following equation:20H, + Ca = 2CaeHo, + HI Water. Calcium. Calcic hydrate. Hydrogen. These last four decompose water with very much less energy than the three first named. The metal Mg requires the water to be heated to a temperature of 55~ C. (122~ F.) before it is able to effect its decomposition. This first method of obtaining hydrogen is not the one practically followed, the expense and difficulty being too great. Potassium acts on the water with so great violence that it is impossible to collect the hydrogen. EXP. 23.-Throw a piece of potassium about the size of a small nut upon the surface of a plate or flat glass dish, filled with water, part of the water is immediately decomposed; each atom of potassium displaces half the hydrogen of an atom of water, and potassic hydrate is formed. 20H2 + K, = 20KH + H, Water. Potassium. Potassic hydrate. Hydrogen. [2H20 + K2 = 2KHO + H] The escaped hydrogen takes fire from the heat resulting from the intensity of the chemical combination, and carrying with it a small portion of the volatilized metal, burns with a reddish violet 68 INORGANIC CHEMISTRY. flame; the metal melts and swims about rapidly upon the water, and finally disappears with an explosive burst of violence, as the globule of melted potassic hydrate which is formed during its oxidation becomes sufficiently cool to come into contact with the water. The action of sodium on the water is the same as that of potassium, sodic hydrate is formed, which being soluble, is immediately dissolved, and hydrogen is set free, as in the following equation:20H, + Na2 = 2ONaH + H, Water. Sodium. Sodic Hydrate. Hydrogen. [2H20 + Na2 = 2NaHO + H2] Sodium does not, however, act with the same energy as potassium, and consequently the evolved gas does not take fire, unless the water be warm, or the sodium be confined to one place, by wrapping it in a piece of filtering paper, previous to throwing it on the water. Advantage is taken of this to collect the hydrogen evolved, as in the following experimentEXP. 24.-Take a piece of sodium as large as a pea, place it securely in a small wire-gauze box, or wrap it tightly in wire gauze firmly fastened'^^. i^ I~to the end of a wire ~;,/?f. ~ ~(A, fig. 8), and hold it Io_, X~' I~ under an inverted cylinder or gas jar (B) filled with water, and i1; 11olstanding on a beehive shelf. The bubbles of hydrogen gas ___j ~ascend in the cylinder and displace the water. When the cylinder is full, it may be Fig. 8. put on one side for future examination of the properties of the gas. This mode of obtaining hydrogen is too expensive, too troublesome, and too dangerous, to be used otherwise than as an experiment of demonstration. PREPARATION OP HYDROGEN. C9 (2.) A second method of obtaining lhydrogen, is by the action of sodium on dryhydrochloric acid. The reaction which takes place is represented by the following equation2HC1 + Na2 = 2NaC1 + H2 Hydrochloric acid. Sodium. Sodic chloride. Hydrogen. (3.) Hydrogen may be prepared very simply and cheaply in large quantities by passing steam over iron filings, or turnings, or even iron nails, maintained at a red heat. The hydrogen so prepared contains a deal of moisture, and therefore if it is required to be dry it must be passed through tubes containing chloride of calcium. The reaction is as follows Fe, + 4OH2 iv(e 3)viiiO + 4H2 Iron. Water. Triferric tetroxide or magnetic oxide of iron. [3Fe + 4H20 = Fe30, + Hs The graphic formula for I(Fe) viii 0 is If a small quantity of hydrogen only be required, or it be merely wanted to demonstrate this method of obtaining it, the arrangement shown in fig. 9 may be adopted..-Fill. 9. Fig. 9. EXP. 25. -A is a flask containing water boiling briskly by the aid of a Bunsen burner or spirit lamp, and connected by a bent tube 70 INORGANIC CHEMISTRY. with a piece of combustion tube B, from 9 to 15 inches long, and about i of an inch in diameter, in which is placed about an ounce of iron filings, which are heated to redness by means of a Bunsen burner; C is the delivery tube, and D the receiver, standing inverted, over a pneumatic trough. When a large quantity of hydrogen is required, an arrangement similar to that shown in fig. 10 must be made, in which the I a Fig, 10. glass combustion tube is replaced by an iron gun barrel, or, better still, by a Berlin porcelain combustion tube; and the source of heat, either a fire-clay furnace, heated with charcoal, as shown in the figure, or a gas combustion furnace especially formed for tube operations. The U-tube filled with calcic chloride is simply for drying the gas. One litre of water converted into steam will yield about 1,240 litres, or 1'24 cubic metre of hydrogen. (4.) The most common method of preparing hydrogen is by the action of metals on water in presence of an acid; the metal most commonly employed is zinc, and the acid, sulphuric; but iron may and sometimes does take the place of zinc, and hydrochloric acid may replace in like manner the sulphuric. Zinc and sulphuric acid is, however, almost universally employed on account of its greater cheapness and also that it yields the gas purer than either of the other combinations. The reactions that take place will be respectively represented in the following equations: PREPARATION OP IIYDROGEN.' (1.) S0OHo2 + Zn = SOZno" + H2 Sulphuric acid. Zinc. Zincic sulphate. Hydrogen. [H2SO4 + Zn = ZnSO4 + H2] (2.) 2HC1 + Zn = nC1l + Ht Hydrochloric acid. Zinc. Zincic chloride. [2HC1 + Zn = ZnCI2 + 112] (3.) S02Hoa + Fe - SO,Feo" + I2 Ferrous sulphate. [HISO4 + Fe = FeSO, + H2] (4.) 2HIC1 + Fe = Fe"C12 + I2 Ferrous chloride. [2EC1 + Fe = FcCIe + It The preparation of hydrogen from zinc and sulphuric acid is conducted as follows: EXP. 26.-A generating flask, A, fig. 11, having a capacity of about a pint, and also a somewhat wide mouth, is chosen; to this a good sound soft cork is fitted, through which pass two tubesone, a short right-angled one, open at both ends; the other, a straight one, terminated by a funnel, called a thistle-headed funnel, which should pass down nearly to the bottom of the flask. By means of a piece of caoutchouc tubing, the right-angled tube may be attached to one, and therefore to any num- ber, of washing bottles,* which' may contain water or any reagent, through which it is advisable for i{ ^tI the gas to pass, to separate any'!l impurities which may be associated with it. In the generating flask, A, should be placed some fragments * Washing bottles are simply ordinary wide-mouthed bottles fitted with corks, through which pass two tubes, each bent at a 72 INORGANIC CHEMISTRY. or cuttings of zinc, or better still, some granulated zinc, (which is made by melting the zinc in an iron ladle, and pouring it from a height of three or four feet into a pail of cold water), then pour into the gas bottle some dilute sulphuric acid, 1 of acid to 7 or 8 of water. (Great care is necessary in mixing the acid and water; the water should be placed in a thin glass beaker and the acid added gradually, great heat being evolved during the mixing. The dilute acid should not be used until it has cooled). Thezincshouldbe covered to the depth of three or four inches. In a short time a brisk effervescence will be observed due to the escape of bubbles of hydrogen. The gas which at first comes off is, of course, contaminated with the atmospheric air contained in the generating flask, and is then dangerously explosive; after a short time, however, this will be all driven away, and the gas will be given off pure. To ascertain when this is the case, collect some of the gas from time to time in a small eprouvette, and apply a light to it; if it explodes or lights with a kind of whistling pop there is air mixed with it, but if it lights with a plain pop and keeps on burning at the mouth of the tube with a pale blue flame, it is pure. Collect at the pneumatic trough as many jars or bottles of gas as may be required to illustrate its properties hereafter described. Should (as frequently happens) the evolution of the gas slacken before all the metal is dissolved, it can be quickened by the addition of a little more acid through the safety funnel. The rationale of what takes place is this: The zinc drives out the hydrogen of the hydric sulphate or sulphuric acid and takes its place, forming zincic sulphate, and setting the hydrogen free; the zincic sulphate, being soluble, is dissolved by the water present, and can be obtained in white crystals from the residue left in the bottle, by simply evaporating the liquid. (5.) Zinc or iron, when boiled with a strong solution of potassic hydrate, displaces the hydrogen. Thus20KH + Zn = ZnKo2 + H Potassic hydrate. Potassic zinc oxide. [2KHO + Zn = ZnO + K20 + H2] right angle, one consisting of a long and a short limb, the other of two short limbs; in the bottle is placed the liquid or other sub stance through which it is intended the gas should pass, and into which the long extremity of the tube C dips, the short tube D conveyingthegas eithertoanotherwashingbottle orto the delivery tube. PREPARATION OF HYDROGEN. 73 (6.) Hydrogen has been prepared on a large scale by the French chemists Deville and Dcbray, by passing steam over charcoal or coke, leated to a dull red heat. Thus20Ha + CiV = Civ2 + 12 Water. Carbonic anhydride. [2H20 + C = CO2 + H11 The carbonic anhydride can be easily removed by passing the gas through a strong solution of potassic hydrate. If, however, the heat be not strictly regulated-if it at all exceed the right degree-another gas, carbonic oxide (Co), which is highly poisonous, is also formed, and this gas cannot be removed. (7.) By the electrolysis of water. On plunging the poles or electrodes of a voltaic battery, consisting of two to four cells of Grove's, or not less than six large cells of Smee's arrangement,' into water slightly acidulated with sulphuric acid, hydrogen is given off at the negative electrode, or that connected with the zinc end of the battery; while oxygen is given off at the positive electrode, or that connected with the carbon or platinum end of the battery. Fig. 12 gives a sketch of the arrangement employed. Fig. 12. A is a battery consisting of six cells of Smee's, the poles * The student should consult the volume on Electricity in this series, or some good manual of Natural Philosophy, for the difference between Grove's and Smee's batteries, and for the chemical action of the electric current. 74 INORGANIC CHEMISTRY. or electrodes of which can be connected with the binding screws of a voltameter, B. These binding screws are connected by wires beneath with electrodes of platinum foil, over which are inverted glass tubes for the collection of the gases separately. It will be observed that the gas in one tube occupies twice the space which that in the other tube does. On testing the gases, that in the first tube will be found to possess all the characteristics of hydrogen, (see page ), and that in the second tube those of oxygen (see page ). This method of procuring hydrogen is also valuable as an analytical experiment, proving that water is compounded of the two gases hydrogen and oxygen in the proportion by volume of 2 to 1; and as the weights of equal volume of H and O are as 1 to 16, it follows that in water they are related to each other by weight in the proportion of 1 to 8. 57. Properties.-Hydrogen is a gas, and as no amount of cold or pressure yet obtained has succeeded in condensing it, it is regarded as one of the permanently elastic gases; it is colourless, tasteless, and inodorous; it is very slightly soluble in water-fifty volumes of water dissolving a little more than one part of the gas; it will not support combustion, in the ordinary sense of the word;; but, in the presence of oxygen or of ordinary atmospheric air, is the most combustible body known. This is, in fact, its chief chemical peculiarity. The sole result of its combustion with O is water. It is the lightest body in nature, its specific gravity being -0692 as compared with air, so that air is 14'4, or about 141 times as heavy as hydrogen. Its great lightness has caused it to be taken as the standard to which the weight of all other gases, simple and compound, is referred. f It also possesses the greatest power of diffusion of all gases. * For a full account of the true theory of combustioni see chapter, page t See paragraph 29, on the " Crith" and its uses. PROPERTIES OF HYDROGEN. 75 (By diffusioz, we are to understand " the tendency of the particles of a gas to separate as far as they can from each other.")5 Hydrogen is not poisonous, and may be breathed once or twice with impunity; but, if continued, it is fatal. This proves, therefore, that it cannot support life any more than it can combustion. The properties of hydrogen may be demonstrated by the following experiments:The absence of colour, taste, and odour may at once be detected by simple in- spection of a jar of the gas. (It does frequently happen that the hydrogen obtained by ordinary methods, and not carefully purified, has a very disagreeable smell. This is caused by the presence of small quantities of sulphur, arsenic, or carbon, present as impurities in the i zinc, which form, with hydrogen, volatile. compounds of a disagreeable odour. If: |!. the zinc and sulphuric acid be perfectly jj pure, no odour whatever is perceived.) EXP. 27.-Its insolubility, or rather very slight solubility, may be inferred from the fact that it can be collected at i the pneumatic trough, without any per- l ceptible loss of the gas; but it may be i accurately measured by taking a gradlu- ated glass tube, and having put in fifty I measures of water, inverting it over the _ mercurial pneumatic trough (fig. 13); then passing in two or three measures — = of hydrogen, no means whatever will make the water absorb more than one measure of the gas. That hydrogen will not support ordinary combustion, but is itself combustible, may be shown by the following experiment:* Diffusion is now more generally considered as due to the intestine movements of gases, as developed in the kynetic theory of gases; for a full consideration of this, see Prof. Clarke Max well's Theory of Heat, Chap. XXIII, page 281, et seq. 76 INORGANIC CHEMISTRY, EXP. 28.-Take a jar of hydrogen, and holding it mouth downwards on account of its lightness, pass by means of a bent wire a lighted taper into it (fig. 14). The gas itself will take fire at the mouth of the jar where it is in contact with the air, but the taper will go out. (Mr. Barrett states, in the Philosophical Magal zine, that the blue appearance of the flame is due to the presence of sulphur, either in the gas, or in the dust of the air in which it burns.) buie The flame of hydrogen is a pale blue, almost invisible one; and the product, when burnt in air or oxygen gas, is water: and nothing but water. Fig. 14. This may be shown in several ways. EXP. 29.-If a clean, cold, dry tumbler or beaker be held over a jet of burning hydrogen, its sides will be almost immediately covered with dew, caused by the condensation of the vapour of water formed by burning hydrogen in the oxygen of the air. EXP. 30.-It may, however, be more conclusively shown, and the water actually collected, by the following arrangement shown in fig. 15:-a is a tube to contain chloride of calcium to dry the Fig. 15. hydrogen gas; b, an infusible glass jet at which the gas is burnt; c, an infusible glass connecting tube; e, the condensing tube in the bend of which the water collects; h, a test tube filled with cold water to condense the water formed by the gas. An appreciable quantity of water will be collected at e, in the course of five minutes; but, if the flame (which should be about half an inch long) be kept steadily burning for about half an hour, a considerable quantity of water will be collected. The tube, a, PROPERTIES OF HYDROGEN. 77 should be connected (fig. 15) with the ordinary generating bottle shown in fig. 10. In exactly the same manner water may be collected (although not in so large a quantity) from the burning of any combustible body which has hydro-, l gen in its composition, such as alcohol, oil, coal gas, &c. The reaction that takes place is precisely identical in all cases. The hydrogen of the burning body unites with the oxygen of the atmosphere to form water, gas, or vapour of water. This, striking on the cold sides of the glass, becomes condensed to the liquid condi- _- L tion.' The lightness of hydrogen may be _. demonstrated by a variety of experiments:- Fig. 16. EXP. 31.-If a jar of hydrogen be collected at the pneumatic trough, it may be removed, mouth downwards, and held in that position A for several minutes, without any stopper, and, on the application of a light, the gas will take fire with a very slight explosion, showing that very little hydrogen has escaped; but, if the jar be removed mouth upwards, the escape of the gas is almost instantaneous, as may be demonstrated by the application of a light. EXP. 32.-On account of its lightness, hydrogen may be collected by upward displacement, as shown in fig. 16. The delivery tube, a, should pass upwards almost to the top of the jar. B EXP. 33.-It may also, from the same cause, be decanted upwards, as shown Fig. 17. in fig. 17. If an empty jar, A, be taken and held with its mouth downwards, and a jar of the gas, B, be carefully brought into the position shown in the figure, the hydrogen will pass from B into A, in the direction shown by the arrow, and dis. 78 INORGANIC CHEMISTRY. place the air in A. If the experiment has been performed neatly, on applying a light to the jar B, it will be found to be entirely free from hydrogen; but, on applying it to the jar A, a slight explosion takes place, showing that A, which only contained air, now contains a mixture of hydrogen and air, which is very explosive. A small balloon, made of goldbeater's skin, will, if filled with dry hydrogen, ascend in the air, thus proving the lightness of the gas. And, finally, its lightness may be easily demonstrated by actual weighing. If a large dry beaker glass be very accurately weighed in scales that will turn with a grain, then filled with hydrogen by upward displacement, and placed mouth downwards on the scales, it will be found to be sensibly and measurably lighter that it was at first when filled with air. 58. Diffusion.-This has been defined to be "the tendency of the particles of a gas to separate from each other as far as they possibly can." This power of diffusion has been found to depend on the density of the gas, being greatest in those of least density; and a series of most carefully conducted and accurate experiments, by Mr. Graham, has succeeded in establishing the following lawv: "The velocity of diffusion of different gases is inversely proportional to the square ll roots of their densities." I: Thus, the densities of IH and O being respectively 1 and 16, the square roots of which numbers are 1 and 4, their rates of l diffusion will be respectively 1 and j —i.e., H I will diffuse with four times the velocity of O. The great difference between the density of H and all other gases, makes it particularly suitable for demonstrating this property by experiment. Fig. 18. EXP. 34.-Take a glass cylinder, from 10 to 12 inches long, and from 1 to 2 inches in diameter; close DIFFUSION AND COMBINATIONS. 79 one end with a plug of plaster of Paris, from i to H inch thick; cover the plaster of Paris end with a plate of glass, and fill the tube with hydrogen by upward displacement; insert the lower end in a glass vessel of coloured water (fig. 18), and remove the glass plate from the top, the hydrogen will pass out so much more quickly than air can pass in, that the coloured liquid will rise in the cylinder to the height of 2 or 3 inches. EXP. 35.-The converse of this may be shown (fig. 19) by taking a porous cylinder (such as those used for galvanic batteries), and fitting to its open end, by means of a bung, a tube about 3 feet i long, and ~ inch in diameter. (Great care is necessary that the bung should be made air-tight by coating it with sealing-wax dissolved in spirits of wine.) This tube is then supported in a vertical position, so that its open extremity shall dip about an inch below the surface of some coloured water in a glass vessel. A bell-jar of hydrogen is then held over the porous cylinder, when the diffusive power of the hydrogen is made manifest by the expulsion of the air in the tube and its bubbling up ~ through the water, caused by so much more hydrogen having entered the porous cell than the air which passed out. If the bell-jar be now removed, after all the bubbling up of the air has ceased, the hydrogen will in like manner escape from the porous cell, and the coloured water will rise in the tube to the height of 10 or 20 inches. If the experiment be repeated, substituting for the hydrogen _ a jar of carbonic acid or coal gas, it will be... found that the heavier the gas the less will it pass through the porous cell, thus proving the truth of the general principle of diffusion. Fig. 19. Hydrogen, in consequence of its exceeding rareness, has a peculiar effect on sound. EXP. 36.-Fill a bell-jar with hydrogen by upward displacement, suspend it to a retort-stand, and strike a bell in it (fig. 20), scarcely any sound will be heard. EXP. 37.-If a deep inspiration of hydrogen be taken (this may be safely done two or even three times) it will change the deepest bass voice into the thin shrill treWe of a child. 59. Combinations.-The compounds which hydrogen 80 INORGANIC CHEMISTRY. forms with the various elements treated of in this little work are as follows:With chlorine, only one, hydrochloric acid, HC1. With oxygen, two, viz., water, HO, and hydroxyl, 1H202. With carbon, hydrogen t I^ iforms many compounds called generically hydrocarbons. The full consideration of these belongs to organic chemistry; but two are sufficiently common and of sufficient importance to be noticed here, viz.:_ -.~ — ~ ~ -___ -^ ~ Marsh gas, or light car. y - = eted' buretted hydrogen, Civl4.,______B________ Olefiant gas, or heavy car... —...a ==~ buretted hydrogen, CivH4. With nitrogen, it forms but Fig. 20. onecompound,ammonia,NH,. With sulphur, it forms two compounds-sulphuretted hydrogen, SH2, and hydrosulphyl,'S',H2 or Hs2. The full consideration of these compounds will be reserved until the elements with which the hydrogen combines shall have been respectively considered. 60. Arithmetical Considerations.-One grain of hydrogen, at the normal temperature of 32~ F. or 0~ C., and pressure of barometer 30 inches or 760 m.m., measures 44-4 cubic inches; and one gramme, at the same normal temperature and pressure, measures 11'2 litres. The atomic weight of hydrogen being 1, it will require 39 grains or grammes of potassium, or 23 grains or grammes of sodium, to set free 1 grain or gramme of hydrogen. So again, zinc and iron being dyad metals, 56 grains or grammes of iron, or 65 grains or grammes of zinc, will liberate 2 grains or grammes of hydrogen HYDROGEN A METAL. 81 So again, with respect to the acids employed, hydrochloric and sulphuric acids being both entirely decomposed, it is a matter of simple rule of three calculation to ascertain how much must be employed to obtain any given quantity, either by weight or measure of hydrogen. Thus, 36-5 grains or grammes of hydrochloric acid (HC1) will yield 1 grain or gramme of hydrogen; and 98 grains or grammes of sulphuric acid S02,Ho2 [H2S04] will yield 2 grains or grammes of hydrogen. 61. Hydrogen a Metal.-There are good grounds for supposing that, if hydrogen could be solidified, it would be found to be a nretal,-that, in fact, the gas, as we meet with it, is but the vapour of a highly volatile metal. Thus, if the metal palladium, be employed 6ss a as the negative electrode in the voltaic arrangement for the decomposition or electrolysis of water, instead of the hydrogen being set free, it is absorbed by the palladium electrode, with which it forms a veritable alloy; and in this condition it conducts heat and electricity, and is electric, or rather, magnetic, in this respect acting exactly as it would do if it were a metal. Other metals besides palladium, such as platinum and iron, possess this property of absorbing hydrogen, but not to the same extent. This would seem to point out hydrogen as a metal, since. no case of a true alloy has been known except in the case of the combination of a metal r'' with a metal. Another strong argument in support of this view is to be found in the fact that. hydrogen gas possesses the power of con- 1| ducting heat, which other gases do not. The good conductivity of hydrogen may Fig21 be shown by the following experiment:- F 10 E. 82 INORGANIC CHEMISTRY. Exp. 38.-Within a glass tube (fig. 21) is stretched a platinum wire, which is raised to incandescence by an electric current. When air, or any gas other than hydrogen, is passed through the tube from the bladder beneath, the incandescence continues; but it disappears as soon as hydrogen is employed. The heat of the wire is, ia fact, conducted away by the hydrogen. CHAPTER VIII. Chlorine-History-Distribution and Natural HistoryPreparation-Properties-Combinations. Symbol, C12. Atomic weight, 35-5. Molecular weight, 71. Molecular volume, -. 1 litre weighs 35-5 criths. Has been liquefied at 15 -5 0. under a pressure of 4 satmospheres, but has never been solidified. Atomicity,'. Evidence of atomicity, HC1. 62. Synonymes.-Chlorine, from XXpos, green (Davy). jDephlogisticated muriatic acid (Scheele). Oxymuriatic;